0.86.7

Honor the DEFAULT_PK_FIELD_NAME setting (and per-field key_attr) when
resolving existing instances in mutation inputs. Previously _parse_pk read the
input value under key_attr but always looked the instance up by pk=, so
relation inputs and bare-id updates that reference an object by a configured
non-pk field raised DoesNotExist or matched the wrong row. Filters already
honored the setting; mutations now do too. The default pk-based path is
unchanged.

This release was contributed by @ayushin in #928