fix: editing of FlagField via EnumFlagField form field

When attempting to edit an EnumFlagField through a model form (e.g. in django
admin), the form would always be invalid on submit with an invalid_choice error.
This was due to the form attempting to set the model field to a list of enum
members (rather than bitwise-OR'ing the flags together).

This change handles this case by overriding FlagField._coerce_to_value_type and
performing the appropriate bitwise OR there.

Author: crgwbr

src/django_enum/fields.py

@@ -1215,6 +1215,15 @@ def contribute_to_class(
             # for non flag fields
             IntegerField.contribute_to_class(self, cls, name, private_only=private_only)
 
+    def _coerce_to_value_type(self, value: Any) -> Any:
+        if (
+            isinstance(value, list)
+            or isinstance(value, tuple)
+            or isinstance(value, set)
+        ):
+            value = reduce(or_, value)
+        return super()._coerce_to_value_type(value)
+
 
 class SmallIntegerFlagField(FlagField, EnumPositiveSmallIntegerField):
     """