Fixed #21905 -- Add info message if DateField or TimeField use a fixed value
Merge pull request #2346 from Markush2010/ticket21905

Fixed #21905 -- Add info message if DateField or TimeField use a fixed value
Fixed #22648 -- Transform.output_type should respect overridden custom_lookup and custom_transform.

Previously, class lookups from the output_type would be used, but any
changes to custom_lookup or custom_transform would be ignored.
Fixed #22019 -- Added Model.objects reference documentation.
Fixed contrib.gis tests breaking in some edge cases.

The tests would error out with an ImproperlyConfigured error
if the user had psycopg installed but not geos.
Thanks to mcgohier for the report.
Fixed #22634 -- Changed Session and SessionStore to be easily extendable

Introduced abstract base model for Session, and properties enabling
the developer to override session model class used by session store
and the session store class used by the model.