self_url_kwargs should come from object, not schema

[fhriley]

related_url_kwargs are pulled from object data. self_url_kwargs are pulled from schema data. This is inconsistent (I got bit by it the first time I tried using self_url_kwargs). Furthermore, it means that all kwargs used in self_url_kwargs must be serialized as part of the schema, which I don't always want to do. For example:

class Meta:
    type_ = "bars"
    self_url = "/foos/{foo_id}/bars/{bar_id}"
    self_url_kwargs = {"foo_id": "<foo_id>, "bar_id": "<id>"}

I don't want foo_id to be serialized in a bars schema.

[multimeric]

I'm not sure I'm understanding correctly, but is this a duplicate of my issue, #247?

[fhriley]

This looks like the same issue, but #247 is on self_view_kwargs. They should probably be fixed together.