Fixed #23535 -- Updated tutorial to account for default filter added in 5ea34f3f86.
Removed sudo from pip commands in docs.
Merged one_to_one_regress into the one_to_one test package.
Merged custom_columns_regress into the custom_columns test package.
Merged custom_managers_regress into the custom_managers test package.
Fixed #23338 -- Added warning when unique=True on ForeigKey

Added a warning when unique is set to True on a ForeignKey, telling
the user to replace it with a OneToOneField and remove unique=True.
Fixed #23338 -- Added tests and updated documentation