Improve admin-facing email templates (#6216)

* Improve subject lines for admin-facing emails

A few of the current subjects are ambiguous about the expected
action, and some omit context that would help in an inbox preview
(which event, which address). The rewrites bring them closer to
common conventions in modern transactional email (verb-led,
recipient-addressed, with recipient-meaningful variables). Two
themes:

- Action-required emails lead with the action verb. "Reset your
  password", "Confirm event cancellation and bulk refund", and
  "Confirm <address> as a sender address" tell the recipient up
  front what's expected, where "Password recovery", "Bulk-refund
  confirmation" and "Sender address verification" did not.

- Surface the relevant variable when the email is about something
  specific. "Data shredding completed for <event>" is more useful
  than the generic version when an admin manages several events.
  "You've been invited to join <organizer>" names the inviting
  organizer. "Confirm <address> as a sender address" names the
  address.

The remaining rewrites are lighter rewordings. "New sign-in to
your account" replaces "Login from new source detected" because
"source" is jargon a non-technical recipient wouldn't recognise.
"Changes to your account" replaces "Account information changed"
because the possessive frames the email as being about the
recipient's own account.

Also fixes a hardcoded "pretix" in the confirmation-code subject.

* Standardise admin email sign-offs as "Thanks, The <instance> Team"

The current sign-offs ("Best regards, Your <instance> team") have
a formal tone. A review of the last ~20 transactional emails in
my inbox showed most senders use something friendlier:

- Thanks: Deliveroo, Starling Bank, GitHub, Cloudflare
- Thank you: AWS
- Sincerely: Google Workspace

A small minority (e.g., Sentry) had no sign-off at all. "Thanks"
was the most common, and among that group "The <instance> Team"
was the consistent phrasing rather than "Your <instance> team".

Two templates (cancel_confirm, export_failed) didn't have a
sign-off; they now get one for consistency. Notification emails
are deliberately excluded: they're system alerts rather than
direct correspondence.

* Add anti-phishing notice to admin emails containing confirmation codes

Three admin emails send the recipient a confirmation code to
enter back into a form: confirmation_code, email_setup, and
cancel_confirm. Only confirmation_code had an anti-phishing
warning, and its wording was awkward ("Please do never give this
code to another person. Our support team will never ask for this
code.").

This commit standardises the warning across all three:

> Don't share this code with anyone. The <instance> team will
> never ask you for it.

* Add structured details to login-notice email

The single-sentence body ("The login was performed using <agent>
on <os> from <country>.") is replaced with a labelled bullet list:
Time, Browser, Operating system, Device, Country.

Time and Device are new fields. Device is omitted when ua-parser
can't identify the device, Country when GeoIP isn't available,
so the user only sees fields with real values.

* Restructure notification.txt for clearer layout

- Attributes: bullet list instead of paragraph-per-attribute.

- Actions: label gets a colon, URL on its own paragraph (was
  4-space-indented code block).

- Footer: separated by --- and bulleted (manage / disable
  links). "Click here X" phrasing dropped (incidentally moots
  a missing-"to" typo).

- Minor whitespace fix: detail-block endif now matches the
  placement of the rest of the template.

notification.html's footer text is also updated, only to match
the new .txt wording (link labels and intro line). No
structural changes to the HTML template.

* Improve confirmation-code email reason strings

- Drop the redundant "to confirm" opener.

- Replace hardcoded "your pretix account" in email_verify
  with "{instance}".

* Polish admin email body copy

A small wording and formatting pass on the admin email bodies,
in three loosely-grouped themes:

1. Sentence case for body text (previously lowercase after
   "Hello,"), matching standard English convention.

2. Light restructuring where helpful: bullet lists for sets
   of labelled facts; 4-space-indented code blocks for codes
   the recipient is meant to type back.

3. Phrasing polish. Some sentences tightened or shortened.
   Largely matters of taste, but generally read smoother.

---------

Co-authored-by: Raphael Michel <michel@pretix.eu>

src/pretix/control/templates/pretixcontrol/email/confirmation_code.txt

@@ -1,13 +1,13 @@
-{% load i18n %}{% blocktrans with url=url|safe messages=messages|safe %}Hello,
+{% load i18n %}{% blocktrans with code=code reason=reason instance=instance %}Hello,
 
 {{ reason }}
 
     {{ code }}
 
-Please do never give this code to another person. Our support team will never ask for this code.
+Don't share this code with anyone. The {{ instance }} team will never ask you for it.
 
-If this code was not requested by you, please contact us immediately.
+If you didn't request this code, please contact us immediately.
 
-Best regards,
-Your {{ instance }} team
+Thanks,  
+The {{ instance }} Team
 {% endblocktrans %}

src/pretix/control/templates/pretixcontrol/email/email_setup.txt

@@ -1,14 +1,15 @@
-{% load i18n %}{% blocktrans with code=code instance=instance %}Hello,
+{% load i18n %}{% blocktrans with code=code address=address instance=instance %}Hello,
 
-someone requested to use {{ address }} as a sender address on {{ instance }}.
-This will allow them to send emails that are shown to originate from this email address.
-If that was you, please enter the following confirmation code:
+Someone requested to use {{ address }} as a sender address on {{ instance }}. Once verified, emails sent from {{ instance }} can show this address as the sender.
 
-{{ code }}
+If this was you, enter the following code in the setup form:
 
-If this was not requested by you, you can safely ignore this email.
+    {{ code }}
 
-Best regards,  
+Don't share this code with anyone. The {{ instance }} team will never ask you for it.
 
-Your {{ instance }} team
-{% endblocktrans %}
+If you didn't request this, you can safely ignore this email.
+
+Thanks,  
+The {{ instance }} Team
+{% endblocktrans %}

src/pretix/control/templates/pretixcontrol/email/forgot.txt

@@ -1,9 +1,11 @@
 {% load i18n %}{% blocktrans with url=url|safe %}Hello,
 
-you requested a new password. Please go to the following page to reset your password:
+We received a request to reset the password for your {{ instance }} account. To choose a new password, follow the link below:
 
 {{ url }}
 
-Best regards,  
-Your {{ instance }} team
+If you didn't request this, you can safely ignore this email — your password won't change.
+
+Thanks,  
+The {{ instance }} Team
 {% endblocktrans %}

src/pretix/control/templates/pretixcontrol/email/invitation.txt

@@ -1,17 +1,16 @@
 {% load i18n %}{% blocktrans with url=url|safe %}Hello,
 
-you have been invited to a team on {{ instance }}, a platform to perform event
-ticket sales.
+You've been invited to join a team on {{ instance }}, an event ticket sales platform.
 
-Organizer: {{ organizer }}
-Team: {{ team }}
+- Organizer: {{ organizer }}
+- Team: {{ team }}
+
+To accept, follow the link below:
 
-If you want to join that team, just click on the following link:
 {{ url }}
 
-If you do not want to join, you can safely ignore or delete this email.
+If you don't want to join, you can safely ignore this email.
 
-Best regards,  
-
-Your {{ instance }} team
+Thanks,  
+The {{ instance }} Team
 {% endblocktrans %}

src/pretix/control/templates/pretixcontrol/email/login_notice.txt

@@ -1,13 +1,19 @@
-{% load i18n %}{% blocktrans with url=url|safe os=source.os_type agent=source.agent_type %}Hello,
+{% load i18n %}{% blocktrans %}Hello,
 
-a login to your {{ instance }} account from an unusual or new location was detected. The login was performed using {{ agent }} on {{ os }} from {{ country }}.
+We noticed a new sign-in to your {{ instance }} account:
+{% endblocktrans %}
+- {% trans "Time" %}: {{ when }}
+- {% trans "Browser" %}: {{ agent }}
+- {% trans "Operating system" %}: {{ os }}
+{% if device %}- {% trans "Device" %}: {{ device }}
+{% endif %}{% if country %}- {% trans "Country" %}: {{ country }}
+{% endif %}
+{% blocktrans with url=url|safe %}If it was you, no action is needed.
 
-If this was you, you can safely ignore this email.
-
-If this was not you, we recommend that you change your password in your account settings:
+If you don't recognise this sign-in, please change your password immediately:
 
 {{ url }}
 
-Best regards,  
-Your {{ instance }} team
+Thanks,  
+The {{ instance }} Team
 {% endblocktrans %}

src/pretix/control/templates/pretixcontrol/email/security_notice.txt

@@ -1,16 +1,15 @@
 {% load i18n %}{% blocktrans with url=url|safe messages=messages|safe %}Hello,
 
-this is to inform you that the account information of your {{ instance }} account has been
-changed. In particular, the following changes have been performed:
+The following changes were made to your {{ instance }} account:
 
 {{ messages }}
 
-If this change was not performed by you, please contact us immediately.
+If you didn't make these changes, please contact the {{ instance }} support team immediately.
 
-You can review and change your account settings here:
+You can review your account settings here:
 
 {{ url }}
 
-Best regards,  
-Your {{ instance }} team
+Thanks,  
+The {{ instance }} Team
 {% endblocktrans %}

src/pretix/control/views/mailsetup.py

@@ -28,7 +28,7 @@ from django.core.mail import get_connection
 from django.shortcuts import redirect
 from django.utils.crypto import get_random_string
 from django.utils.functional import cached_property
-from django.utils.translation import gettext_lazy as _
+from django.utils.translation import gettext, gettext_lazy as _
 from django.views.generic import TemplateView
 
 from pretix.base import email
@@ -216,13 +216,14 @@ class MailSettingsSetupView(TemplateView):
                     messages.error(request, _('The verification code was incorrect, please try again.'))
                 else:
                     self.request.session[session_key] = get_random_string(length=6, allowed_chars='1234567890')
+                    sender_address = self.simple_form.cleaned_data.get('mail_from')
                     mail(
-                        self.simple_form.cleaned_data.get('mail_from'),
-                        _('Sender address verification'),
+                        sender_address,
+                        gettext('Confirm %(address)s as a sender address') % {'address': sender_address},
                         'pretixcontrol/email/email_setup.txt',
                         {
                             'code': self.request.session[session_key],
-                            'address': self.simple_form.cleaned_data.get('mail_from'),
+                            'address': sender_address,
                             'instance': settings.PRETIX_INSTANCE_NAME,
                         },
                         None,

src/pretix/control/views/organizer.py

@@ -1032,7 +1032,9 @@ class TeamMemberView(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixin,
     def _send_invite(self, instance):
         mail(
             instance.email,
-            _('Account invitation'),
+            gettext('You\'ve been invited to join %(organizer)s') % {
+                'organizer': self.request.organizer.name,
+            },
             'pretixcontrol/email/invitation.txt',
             {
                 'instance': settings.PRETIX_INSTANCE_NAME,