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
Fixed #22783: Make sure swappable models come first in creation
Fixed #22847: Optimizer wasn't expecting unresolved FKs
Added database migration for contrib.contenttypes.

Moved contenttypes tests to allow them to run correctly in the presence of
migrations. refs #22170.