ResourceRelatedField: Support resource_name in to_internal_value

[czosel]

I'm trying to modify the type of a ResourceRelatedField: Instead of the model name, i'd like to serve another name.

For GET requests, that works nicely because to_representation considers resource_name on the serializer (if the field is part of included_serializers).

However, POSTing a new resource under the different resource_name does not work, because to_internal_value considers only the model for expected_relation_type.

Suggestion: Allow passing resource_name to ResourceRelatedField. If specified, it

• is used in to_internal_value to map to the actual resource name (which is read from the queryset)
• should take priority over resource_name on the serializer in to_representation

What do you think? Is there an easier approach to this? I'd be happy to provide a PR if you think this is the way to go.

PS: In case you wonder, our use case for this: We need two different endpoints with different permissions and serializers for the same underlying Django model. (The "owner" of the model sees more than anyone else.)

[czosel]

After giving this some more thought, i noticed that it would make much more sense if to_internal_value works the same way as to_representation: By checking Meta.resource_name on the corresponding serializer. So thats how i implemented it in #306.