Add and update compatibility functions for working with models and fields.
Review Request #12229 — Created April 8, 2022 and submitted
This introduces three new compatibility functions for working with fields
cross-Django:
get_field_is_relation()
get_field_is_many_to_many()
get_remote_field_related_model()
It also updates several other field-relation functions to provide more
consistent results for different fiels and relation types.
Unit tests were added for most functions in this module to help catch
inconsistencies in behavior across versions of Django.
Unit tests pass on all supported versions of Django.
Used the new behavior in some in-progress changes.