Scope grant persistence + diff

[dkarlovi]

If a client requests scope A and it gets granted, we should persist.

If the client requests scope A again, there's no need to display the grant view at all, it's already been granted.

If the client requests scope A B next, we should display the grant screen again, asking the user to grant B (optionally, displaying A was already granted, and when).

TLDR: the grant screen should show up only if there's something new to grant.