Support for multiple coupons with specifc Keycloak group assignation

[marcelovilla]

Is your feature request related to a problem? Please describe.
Currently, all users are assigned to a single Keycloak group, despite of the coupon they use to register.

Describe the solution you'd like
It would be nice to be able to assign users to different groups, depending on the coupon they use to register. This way, permissions and access to different instance types can be easily controlled.

Describe alternatives you've considered
It was suggested before that the configuration could look like:

coupons:
  - ANT:
    - account_expiration: 30
    - groups = [group1, group2]
    - approved_domains = [quansight.com, *.mil]
  - BAT:
    - account_expiration: 7
    - groups = [group3]
    - approved_domains = [*.mil]

Additional context

[kenafoster]

My only concern is with the upgrade path...

I don't think it's good design to have both the old (global coupon parameters) and new config (per-coupon params) formats available (or if it is, we should talk more about how we could possibly format it

I also don't think it's an option for nebari upgrade to hook into extensions and rewrite config specs the way it does for the core Nebari parameters. (I think it would mean a lot of re-architecting... but I guess it wouldn't hurt to ask the board what they think)

The best way is probably include messaging and a link to documentation when the user runs nebari deploy (or render or validate) since the validation will fail if the updated extension runs against the previous config schema