BE: RBAC: Support provider for basic auth

[Haarolean]

Implement RBAC support for basic auth provider

Pros:

• more control than a r/o filter
• no need to integrate oauth provider like keycloak for a single user installation
• no need to support r/o filter anymore?:)

[wernerdv]

Please assign this task to me.

[Haarolean]

@wernerdv kind reminder

[Haarolean]

Seems redundant once #344 is done. Please follow and upvote #344 if you're interested.