Add OGJWTAuthProvider to handle admin users

[joshuadkitenge]

Description

Introduce the OGJWTAuthProvider class to streamline handling of admin users in the OG. This class will provide the isAdmin method to verify if a user has administrative privileges based on the authorised_routes in their JWT.

Tasks

• Implement the OGJWTAuthProvider class, inheriting from JWTAuthProvider, and add the isAdmin method.
  • Ensure isAdmin checks the token's authorised_routes for the presence of '/users GET'.
• Write unit tests for the isAdmin method to cover:
  • No token in localStorage.
  • Token with no or empty authorised_routes.
  • Token containing the '/users GET' route.

Acceptance Criteria

• OGJWTAuthProvider correctly identifies admin status through isAdmin.
• Unit tests validate all possible scenarios for isAdmin.