Prevent Object/Nested from mutating the inner doc_class' mapping

[l1nd3r0th]

If the same inner doc is used with both Object and Nested they override each other's mapping type, as shown in the test.

[twiddli]

This is a pretty subtle but serious issue. I just encountered it. Can this get merged?

I get this error when trying to init as a result of this issue:

elasticsearch.exceptions.RequestError: RequestError(400, 'mapper_parsing_exception', 'Root mapping definition has unsupported parameters:  [type : nested]')

The workaround to this error is to delete the faulty key just before creating the index:
cls._doc_type.mapping._meta.pop('type', None)

[l1nd3r0th]

This is a pretty subtle but serious issue. I just encountered it. Can this get merged?

I'm all for!

Maintainers, if there's something I can help with to get this moving, please let me know.

[sethmlarson]

Thanks for opening this PR and for your patience, this is definitely a bug.