[maint] Resolve failing djmain tests

[n2ygk]

Tox tests are currently failing with djmain. Figure out and resolve before the next Django 4.x release is published and those tests fail too.

[n2ygk]

Also need to change the gh workflow to flag the failures. They are currently buried and don't show up.

[n2ygk]

Something has changed between Django 4.0 and main branch leading to an attempt to do an unsupported SQLIte3 operation:

self = <django.db.backends.sqlite3.base.SQLiteCursorWrapper object at 0x10b8038b0>
query = 'ALTER TABLE "oauth2_provider_accesstoken" ADD COLUMN "source_refresh_token_id" bigint NULL UNIQUE REFERENCES "oauth2_provider_refreshtoken" ("id") DEFERRABLE INITIALLY DEFERRED'
params = []

    def execute(self, query, params=None):
        if params is None:
            return Database.Cursor.execute(self, query)
        query = self.convert_query(query)
>       return Database.Cursor.execute(self, query, params)
E       django.db.utils.OperationalError: Cannot add a UNIQUE column

[n2ygk]

I've opened this upstream Django ticket: https://code.djangoproject.com/ticket/33408

[n2ygk]

Fixed here: django/django#15278

[n2ygk]

Upstream fix has been merged. djmain tests are succeeding again.

gh workflow question is being discussed at https://github.com/orgs/jazzband/teams/django-oauth-toolkit/discussions/2