Merge pull request #2806 from jorgecarleitao/issue22826

Fixed #22826 -- Improved internal usage of Query.setup_joins.
Fixed #22842
Merge pull request #2810 from magrinidiego/ticket_22842_tutorial_test

Fixed #22842
Improve error message for missing migrations in an app
Fixed #22563: Added migration to admin, fixed a few more loader issues.
Fixed #22660: Doc'd you can't have unmigrated apps depend on migrated
Fixed #22833: Autodetector not doing through mapping correctly
Persist non-schema-relevant Meta changes in migrations
Fixed #22470: Full migration support for order_with_respect_to
Fixed #22568: Better proxy model support in migrations
Added database migration for contrib.sites.

refs #22170.
Added database migration for contrib.flatpages.

refs #22170.
Added database migration for contrib.redirects.

refs #22170.
Fixed several flake8 errors
Fixed #22844: Duplicate SQL for SQLite FKs
Removed usaged of contrib.sessions as a placeholder in migration tests.

Without this, we're unable to add actual migrations for the app.
Added database migration for contrib.sessions.

refs #22170.
Fixed #22788 -- Ensured custom migration operations can be written.

This inspects the migration operation, and if it is not in the
django.db.migrations module, it adds the relevant imports to the
migration writer and uses the correct class name.
Use __first__ not __latest__ for unknown app dependencies
Fixed #22848: Ignore no-migrations errors during makemigrations only