Added dashboard restriction into RBAC system

[hfehrmann]

Warning

There is a bug in the current implementation, where if a user has selected a dashboard that is blocked by the RBAC system, the UI doesn't load for them. Current implementation doesn't restrict the dashboard election for the user

Follow up on #20

Adds the capability of restricting dashboards for the user. This implementation attaches itself into the WebsScket API for the panels endpoint.

Giving that the frontend handles the routing logic using the results from that endpoint, a user cannot access a restricted dashboards even if they put the exact match into the URL.

I'm not sure if this is up to standard for the repo

[SamAthanas]

Hey @hfehrmann, thank you for your contribution! This is a great idea.

I just tested your code locally and it seems to not be compatible with the previous configuration, hiding all the panels including the main dashboard. Heres a screenshot of what I am seeing on my side:

If the panel config is empty, can we show all panels by default?

[hfehrmann]

@SamAthanas Oh! I'm gonna try to see how the system manages the migration to the new panels field on the role config.

Having said that, does the role you are showing blocks by default?