Implement OAuth2 provider (#927)

- [x] Application management
  - [x] Link
  - [ ] Tests
- [x] Authorize flow
  - [x] Tests
- [x] Refresh token handling
  - [x] Tests
- [x] Revocation endpoint
  - [x] Tests
  - [x] Mitigate: https://github.com/jazzband/django-oauth-toolkit/issues/585
- [x] API authenticator / permission driver
  - [x] Test
- [x] Enforce organizer restriction
  - [x] Tests
- [x] Enforce scope restriction
  - [x] Tests
- [x] Show current applications to user
  - [x] Revoke
  - [x] Tests
- [x] Log new authorizations
  - [x] notify user
- [x] Ensure other grant types are not available
- [x] Documentation
- [x] check if revoking access toking, then refreshing gets rid of organizer constraint
- [x] Show logentry foo

src/pretix/base/models/base.py

@@ -36,7 +36,7 @@ def cached_file_delete(sender, instance, **kwargs):
 
 class LoggingMixin:
 
-    def log_action(self, action, data=None, user=None, api_token=None, save=True):
+    def log_action(self, action, data=None, user=None, api_token=None, auth=None, save=True):
         """
         Create a LogEntry object that is related to this object.
         See the LogEntry documentation for details.
@@ -47,6 +47,8 @@ class LoggingMixin:
         """
         from .log import LogEntry
         from .event import Event
+        from pretix.api.models import OAuthAccessToken, OAuthApplication
+        from .organizer import TeamAPIToken
         from ..notifications import get_all_notification_types
         from ..services.notifications import notify
 
@@ -57,7 +59,18 @@ class LoggingMixin:
             event = self.event
         if user and not user.is_authenticated:
             user = None
-        logentry = LogEntry(content_object=self, user=user, action_type=action, event=event, api_token=api_token)
+
+        kwargs = {}
+        if isinstance(auth, OAuthAccessToken):
+            kwargs['oauth_application'] = auth.application
+        elif isinstance(auth, OAuthApplication):
+            kwargs['oauth_application'] = auth
+        elif isinstance(auth, TeamAPIToken):
+            kwargs['api_token'] = auth
+        elif isinstance(api_token, TeamAPIToken):
+            kwargs['api_token'] = api_token
+
+        logentry = LogEntry(content_object=self, user=user, action_type=action, event=event, **kwargs)
         if data:
             logentry.data = json.dumps(data, cls=CustomJSONEncoder)
         if save:
@@ -83,4 +96,4 @@ class LoggedModel(models.Model, LoggingMixin):
 
         return LogEntry.objects.filter(
             content_type=ContentType.objects.get_for_model(type(self)), object_id=self.pk
-        ).select_related('user', 'event')
+        ).select_related('user', 'event', 'oauth_application', 'api_token')