Support nested RelatedField

[jheld]

There is a very custom use case in DRF, called RelatedField which subclasses Field and thus sits just a little underneath the usual class hierarchy of Serializer. They are quite similar, but I unfortunately cannot simply plug-n-play a subclass of RelatedField inside a call to NestedField.

So, I'm wondering if there's room to build support in the wiring of NestedField or perhaps to make a new integration point like NestedRelatedField to accommodate this issue.