Filter users

[oguzkocer]

Addresses #29.

This PR implements fields based filtering for /users endpoint, including list, retrieve and retrieve_me variants. It adds a SparseUserField enum and 3 new request builders that take a slice of these fields.

It adds quite a few integration tests using rstest, but it takes less than a second to run all of them, and they give us the peace of mind that filtering is working as expected, so I think it's well worth it.

Note that all tests use the Edit context as they test every single field type and not all fields are available for all contexts. We could add specific tests for Embed & View contexts, but I am not sure there is too much value in that. Let me know what you think!

[crazytonyli]

Is there any plan supporting _fileds in the rest functions(update, create, etc)?

[oguzkocer]

Is there any plan supporting _fields in the rest functions(update, create, etc)?

I don't think so. What do you think @jkmassel?

[jkmassel]

Interesting – I guess you might just want the id back or something from a create or update?

Does that work? Have you tested it against the API?

[oguzkocer]

Does that work? Have you tested it against the API?

@jkmassel It looks like it does - at least for creating users. Would you like me to implement it?

[jkmassel]

We should support it eventually, but I'd say put it on the backlog for now – returning a whole User after creation isn't a huge bandwidth waste – the data is pretty small.

By the time we're doing Post or Comment we might want it for the savings there.

[oguzkocer]

I've created a separate issue for that: #74.