Mail signature (#485)

* added signature field -- no function yet

* added mail signature feature

* fixed style issue

* fixed problem with signature default

* added unit test for mail signatures

* added unit test for mail signatures

src/pretix/control/forms/event.py

@@ -474,6 +474,15 @@ class MailSettingsForm(SettingsForm):
         label=_("Sender address"),
         help_text=_("Sender address for outgoing emails")
     )
+
+    mail_text_signature = I18nFormField(
+        label=_("Signature"),
+        required=False,
+        widget=I18nTextarea,
+        help_text=_("This will be attached to every email. Available placeholders: {event}"),
+        validators=[PlaceholderValidator(['{event}'])]
+    )
+
     mail_text_order_placed = I18nFormField(
         label=_("Text"),
         required=False,

src/pretix/control/templates/pretixcontrol/event/mail.html

@@ -10,6 +10,7 @@
             <legend>{% trans "E-mail settings" %}</legend>
             {% bootstrap_field form.mail_prefix layout="horizontal" %}
             {% bootstrap_field form.mail_from layout="horizontal" %}
+            {% bootstrap_field form.mail_text_signature layout="horizontal" %}
         </fieldset>
         <fieldset>
             <legend>{% trans "E-mail content" %}</legend>