Arvados

I observed that several endpoints (users, collections) don't return the documented 'href' field. It seems likely they have not returned this field for a long time (since controller started intercepting these requests), but nobody noticed because nobody relies on it.

On the other hand, some endpoints (workflows, groups) do still return 'href'.

The 'href' field is a synthetic field (not stored in the database) and not very useful because it contains information that can be inferred from the 'uuid' field. (In theory, it could be useful for writing a generic client that doesn't need to understand how the arvados uuid scheme maps to API endpoints, but we've never wanted to do anything like that in practice.)

This was overlooked in the previous cleanup ticket, but the time to make API changes like this is now, before the 3.0 release.

We can save a few bytes if we get rid of this field from the response entirely.