Remove the UserResource-specific ETag serialization.
Review Request #7080 — Created March 18, 2015 and submitted
We had a custom get_etag from a long while back that generated an ETag without the private profile information. This generated warnings against modern Djblets, and it also broke when a subclass was placed in a resource with URL keyword arguments, since kwargs wasn't passed down. This function isn't needed anymore, since ETag generation is now based on the serialized resource (which, for this resource, already filters the contents for any private information), and the result is encoded.
Unit tests pass.
RBCommons no longer breaks when trying to access a subclass of this resource.