[Backend] Make Scopes/Roles easier to use in the UI

[pattisdr]

Is your feature request related to a specific problem?

I believe we need to return scopes as enum types to make it easier for the UI to stay up to date. Also, it would be useful to have a list of all scopes the user has via any avenue.

Describe the solution you'd like

• Add total_scopes key to get_user_permissions. This should return a combination of scopes the user has been assigned directly along with any scopes they have via their role(s). There shouldn't be duplicates here.
• get_user_permissions scopes and total_scopes type should be an enum. Context here: [Backend] Add Role-Based Permissions [#2606] #2671 (comment)

Describe alternatives you've considered, if any

A description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.