Fix: Keycloak Refresh Tokens before Expiry

[GODrums]

Motivation

Currently, users are forced to refresh the Hephaestus-Website (every 30 minutes) when the access token expires and subsequent requests include invalid authentication/JWT token.

Description

This PR fixes the token expiry issue by adding a refresh interval checking for expiry every 60 seconds. Keycloak then refreshes the token itself (triggers a new request to the Keycloak-server).

The PR implements ideas from this best practices guide: https://github.com/akoserwal/keycloak-integrations/blob/main/angular-keycloak/src/main.ts

Additional security suggestions from this Medium article could indepently used for higher security.

Testing Instructions

• Run application-server and webapp
• Login on the website
• Wait for the set accessTokenValidity set in the Keycloak Admin Interface (previously 30min)
• Check if new requests, e.g. switching the leaderboard, still load

Screenshots (if applicable)

Checklist

General

• PR title is clear and descriptive
• PR description explains the purpose and changes
• Code follows project coding standards
• Self-review of the code has been done
• Changes have been tested locally
• Screenshots have been attached (if applicable)
• Documentation has been updated (if applicable)

[FelixTJDietrich]

Thanks a lot for fixing this!