Finish and update users/roles/registration-keys management UI

[NicoBiernat]

In the Admin section, we need to finish the CRUD management UIs for Users, Roles, Registration-Keys.

The Users UI is almost done, but requires some modification for the REST API changes to API-tokens.

Roles and Registration-Keys don't have any Modals for Add, View, Edit and Delete yet.
We also have to think about how we want to add/remove users to/from roles.

And how do we show API tokens of other users?
-> This is very helpful for admins to get tokens of deploy users (e.g. Live) without having to login as that user.

[fwcd]

And how do we show API tokens of other users?

My initial idea with the current design was that this button shows (and potentially cycles) the API key of the user whose display is shown:

...and that this button always shows the user's own API key:

(That's also why the API token card was supposed to be hidden for all other displays for all non-admin users)

[NicoBiernat]

My first idea was to integrate API token management into the users table and modals in the admin area.
But your idea sounds better 👍 (or we could add both)
There should also be an option (only for admins) to make this token permanent via PUT /users/<id>/api-token with payload { "permanent": true/false }