♻️(frontend) switch to Authorization Code flow

Instead of interacting with Keycloak, the frontend navigate to the
/authenticate endpoint, which starts the Authorization code flow.

When the flow is done, the backend redirect back to the SPA,
passing a session cookie and a csrf cookie.

Done:
- Query GET user/me to determine if user is authenticated yet
- Remove Keycloak js dependency, as all the OIDC logic is handled by the backend
- Store user's data instead of the JWT token

src/frontend/apps/desk/.env.development

@@ -1,5 +1 @@
 NEXT_PUBLIC_API_URL=http://localhost:8071/api/v1.0/
-NEXT_PUBLIC_KEYCLOAK_URL=http://localhost:8080/
-NEXT_PUBLIC_KEYCLOAK_REALM=people
-NEXT_PUBLIC_KEYCLOAK_CLIENT_ID=people-front
-NEXT_PUBLIC_KEYCLOAK_LOGIN=true