Present all scopes supported by the server, as well as those requested

When granting consent, it can be super useful to know what other scopes could be granted at the same time, i.e draft for when we want to force clients to not be allowed to publish posts that will be public, yet.

We can do this by adding a Scope.Group which helps keep scopes together, and categorise scopes we already knew about, and a few new ones that are either known about (READING, PUBLISHING) or proposed by me (NOTIFICATION).

In our consent endpoint, we go through the scopes that the client requested, and combine it with the scopes understood by the server.

Anything that isn't understood is separately presented, so it's a bit clearer that it's not know of.

Closes #295 (closed).