feat: Add Support for Roles in User Impersonation

[dthyresson]

The current Studio GraphiQL config with User Impersonation does not set roles:

 type AuthImpersonationConfig {
    authProvider: String
    userId: String
    email: String
    # TODO: Add support for roles <<-------
    # roles: [String]
    jwtSecret: String
  }

And generateAuthHeaders in api/src/services/graphiql/graphiql.ts does not set or use these.

This means that devs cannot try out role access in the api/service layer.