Fixed #21832 -- Updated prompt, tests, and docs to show that USERNAME_FIELD supports FK after 9bc2d76.

Also added get_input_data() hook in createsuperuser.

Thanks Chris Jerdonek and Tim Graham for review.
Fixed #22978 -- Removed a USA-centric example that didn't add much.
Added a unit test to ensure models cannot be ordered by a M2M field.
Document -l as well as --list on migrate
Fixed #22812 -- Refactored lookup API documentation.

Thanks Anssi and Tim for reviews.