moving from built idp in to keycloak causes settings service to fail #670

Describe the bug

A clear and concise description of what the bug is.

Steps to reproduce

1. deploy docker compose full example without keycloak, login should work
2. configure external keycloak in .env
3. restart deployment with docker compose up -d to pick up new env

Expected behavior

login should work

Actual behavior

The container fails to start. The admin user ID has not been configured for settings...

Additional info

OC_ADMIN_USER_ID is set to "" when keycloak is enabled, but it was set in the initial deployment with the build in idp. Maybe the settings service stores that somewhere.

Maybe SETTINGS_SETUP_DEFAULT_ASSIGNMENTS needs to be set to false:

	if cfg.SetupDefaultAssignments && cfg.AdminUserID == "" {
		return shared.MissingAdminUserID(cfg.Service.Name)
	}

Thet means that the env file must have DEMO_USERS=false. We could add that to the keycloak.yml