Invalid keycloak auth url for login

[jet-go]

Issue Summary
Same issue as alerta/alerta#1808. Necessary changes also needs to be done on front end.

Environment

• OS: [Linux, Mac, Windows]

• API version: 9.0.0

• Deployment: Docker

• For self-hosted, WSGI environment: nginx/uwsgi

• Server config:
  Auth enabled? Yes
  Auth provider? Keycloak
  Customer views? Yes
  (or provide the /config endpoint output)

• web UI version: 8.7.0

• CLI version: 8.5.2

To Reproduce
Steps to reproduce the behaviour:

1. Deploy keycloak 17+ with defaults.
2. Run alerta with keycloak as auth provider.
3. Alerta server should have the KEYCLOAK_URL set to http://<kc-url>/auth.
4. Run alerta-webui.
5. When we try to access, the url is redirected to http://<kc-url>/auth/auth/realms/... for login.

Expected behavior
Remove /auth from authorization Endpoint.
https://github.com/alerta/alerta-webui/blob/master/src/services/auth.ts#L85

[tbbkitty]

Got around this by just using the openid config as this is more "clean"

See: alerta/docker-alerta#463 (comment)