Dynamic token management with TokenManager

[Prakhar896]

Overview of changes:

• Added new TokenManager service to consolidate the signing, verification and refreshing of JWTs
• validateToken middleware now uses TokenManager to dynamically verify tokens in requests and refresh tokens that are expiring in 10 minutes or less.
• validateToken will insert a refreshedtoken header in the response if the token is refreshed for the frontend to replace the expiring JWT with this new JWT
• Wrote documentation for the additions to the authentication system and how to implement it for other devs

Sensitive changes:

• Frontend devs will need to update some of the request code as outlined in the Authentication System in the newly written ConfiguringSystem.md documentation

[Prakhar896]

LGTU