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/tests/presale/test_orders.py

@@ -273,6 +273,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-attendee_name_parts_0' % self.ticket_pos.id: '',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -304,6 +305,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-attendee_name_parts_0' % self.ticket_pos.id: 'Peter',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response, '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
                                                                 self.order.secret),
@@ -326,6 +328,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-question_%s' % (self.ticket_pos.id, self.question.id): '',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -350,6 +353,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-question_%s' % (self.ticket_pos.id, self.question.id): '',
+                'transmission_type': 'email',
             }, follow=True)
         doc = BeautifulSoup(response.content.decode(), "lxml")
         self.assertGreaterEqual(len(doc.select('.has-error')), 1)
@@ -357,6 +361,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-question_%s' % (self.ticket_pos.id, self.question.id): 'ABC',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -374,6 +379,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-question_%s' % (self.ticket_pos.id, self.question.id): 'ABC',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -390,6 +396,7 @@ class OrdersTest(BaseOrdersTest):
                 'street': 'Main Street',
                 'city': 'Heidelberg',
                 'country': 'DE',
+                'transmission_type': 'email',
             }, follow=True)
         doc = BeautifulSoup(response.content.decode(), "lxml")
         self.assertGreaterEqual(len(doc.select('.has-error')), 1)
@@ -403,6 +410,7 @@ class OrdersTest(BaseOrdersTest):
         response = self.client.post(
             '/%s/%s/order/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
                 '%s-question_%s' % (self.ticket_pos.id, self.question.id): 'ABC',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -419,6 +427,7 @@ class OrdersTest(BaseOrdersTest):
                 'street': 'Main Street',
                 'city': 'Heidelberg',
                 'country': 'DE',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -436,6 +445,7 @@ class OrdersTest(BaseOrdersTest):
                 'street': 'Main Street',
                 'city': 'Heidelberg',
                 'country': 'DE',
+                'transmission_type': 'email',
             }, follow=True)
         self.assertRedirects(response,
                              '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
@@ -477,8 +487,12 @@ class OrdersTest(BaseOrdersTest):
         # Not all fields filled out, expect success
         response = self.client.post(
             '/%s/%s/ticket/%s/%s/%s/modify' % (self.orga.slug, self.event.slug, self.order.code,
-                                               self.ticket_pos.positionid, self.ticket_pos.web_secret)
+                                               self.ticket_pos.positionid, self.ticket_pos.web_secret),
+            {
+                'transmission_type': 'email',
+            }
         )
+        print(response.content.decode())
         self.assertRedirects(response,
                              '/%s/%s/ticket/%s/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
                                                           self.ticket_pos.positionid, self.ticket_pos.web_secret),