GetRoles without Custom Authentication Requirement

**Is your feature request related to a problem? Please describe.**

The [tutorial](https://docs.microsoft.com/en-us/azure/static-web-apps/assign-roles-microsoft-graph) provided requires an _Azure Active Directory_. The [documentation](https://docs.microsoft.com/en-us/azure/static-web-apps/authentication-authorization?tabs=function) states that _The ability to assign roles via a function is only available when [custom authentication](https://docs.microsoft.com/en-us/azure/static-web-apps/authentication-custom) is configured_.

My scenario is very simple. I would like to be able to _'Query a database to determine which roles a user should be assigned'_ as stated in the [documentation](https://docs.microsoft.com/en-us/azure/static-web-apps/authentication-authorization?tabs=function).

**Describe the solution you'd like**

The ability to use this functionality without the need for [custom authentication](https://docs.microsoft.com/en-us/azure/static-web-apps/authentication-custom).

The authentication service provided by SWA and it's built in providers removes that burden from the developer. Managing the roles for a small number of users could easily be handled in the backend.

**Describe alternatives you've considered**

1. [Using OpenID Connect](https://docs.microsoft.com/en-us/azure/static-web-apps/authentication-custom?tabs=openid-connect)/[Auth0](https://auth0.com/)- feels like overkill for my requirements.
2. Adding claims - have not attempted yet.

**Additional context**