Pluggable invoice transmission methods (#5020)

* Flexible invoice transmission

* UI work

* Add peppol and output

* API support

* Profile integration

* Simplify form for individuals

* Remove sent_to_customer usage

* more steps

* Revert "Bank transfer: Allow to send the invoice direclty to the accounting department (#2975)"

This reverts commit cea6c340be.

* minor fixes

* Fixes after rebase

* update stati

* Backend view

* Transmit and show status

* status, retransmission

* API retransmission

* More fields

* API docs

* Plugin docs

* Update migration

* Add missing license headers

* Remove dead code, fix current tests

* Run isort

* Update regex

* Rebase migration

* Fix migration

* Add tests, fix bugs

* Rebase migration

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Make migration reversible

* Add TransmissionType.enforce_transmission

* Fix registries API usage after rebase

* Remove code I forgot to delete

* Update transmission status display depending on type

* Add testmode_supported

* Update src/pretix/static/pretixbase/js/addressform.js

Co-authored-by: luelista <weller@rami.io>

* Update src/pretix/static/pretixbase/js/addressform.js

Co-authored-by: luelista <weller@rami.io>

* Update src/pretix/static/pretixbase/js/addressform.js

Co-authored-by: luelista <weller@rami.io>

* New mechanism for non-required invoice forms

* Update src/pretix/base/invoicing/transmission.py

Co-authored-by: luelista <weller@rami.io>

* Declare testmode_supported for email

* Make transmission_email_other an implementation detail

* Fix failing tests and add new ones

* Update src/pretix/base/services/invoices.py

Co-authored-by: luelista <weller@rami.io>

* Add emails to email history

* Fix comma error

* More generic default email text

* Cleanup

* Remove "email invoices" button and refine logic

* Rebase migration

* Fix edge case

---------

Co-authored-by: luelista <weller@rami.io>

src/pretix/control/logdisplay.py

@@ -524,6 +524,11 @@ def pretixcontrol_orderposition_blocked_display(sender: Event, orderposition, bl
     'pretix.event.order.invoice.generated': _('The invoice has been generated.'),
     'pretix.event.order.invoice.regenerated': _('The invoice has been regenerated.'),
     'pretix.event.order.invoice.reissued': _('The invoice has been reissued.'),
+    'pretix.event.order.invoice.sent': _('The invoice {full_invoice_no} has been sent.'),
+    'pretix.event.order.invoice.sending_failed': _('The transmission of invoice {full_invoice_no} has failed.'),
+    'pretix.event.order.invoice.testmode_ignored': _('Invoice {full_invoice_no} has not been transmitted because '
+                                                     'no transmission provider supports test mode invoices.'),
+    'pretix.event.order.invoice.retransmitted': _('The invoice {full_invoice_no} has been scheduled for retransmission.'),
     'pretix.event.order.comment': _('The order\'s internal comment has been updated.'),
     'pretix.event.order.custom_followup_at': _('The order\'s follow-up date has been updated.'),
     'pretix.event.order.checkin_attention': _('The order\'s flag to require attention at check-in has been '
@@ -536,6 +541,7 @@ def pretixcontrol_orderposition_blocked_display(sender: Event, orderposition, bl
     'pretix.event.order.email.error': _('Sending of an email has failed.'),
     'pretix.event.order.email.attachments.skipped': _('The email has been sent without attached tickets since they '
                                                       'would have been too large to be likely to arrive.'),
+    'pretix.event.order.email.invoice': _('An invoice email has been sent.'),
     'pretix.event.order.email.custom_sent': _('A custom email has been sent.'),
     'pretix.event.order.position.email.custom_sent': _('A custom email has been sent to an attendee.'),
     'pretix.event.order.email.download_reminder_sent': _('An email has been sent with a reminder that the ticket '