[ENH] - Add a default keycloak role to allow app sharing for convenience

[aktech]

Feature description

We recently added ability to configure fine-grained permissions for JupyterHub via keycloak here: #2471

Add a default keycloak role in the jupyterhub client to be allow app sharing.

Scopes: shares!user,read:users:name,read:groups:name

Value and/or benefit

Users can create it themselves as well, but would be nice to provide this auto-created, so that users can directly assign this role to users to allow them to share apps via jhub-apps in Nebari.

Anything else?

No response