Auth with Keycloak

[zelytra]

We're going to implement aBasic authentification system to add security to the application. Only essential user information will be requested from the user:

• Email: For unique user identification, provided by default by Microsoft without any additional authorization.
• Username: To display the player's username within the app.

That's it for now! (Note that this may be updated in the future.)

Todo :

• Implement Keycloak
• Add frontend authentification workflow
• Add visual authentification to the frontend
• Update the username system in the frontend
• Secure the websocket and the rout of the backend
• Update UT of the backend (mock auth sys)
• Add custom badge for beta tester and contributor basing on the pseudo, hadcoded in a json list

Closes #118
Closes #120
Fix #185
Fix #198