Enable Alerta authentication by default.

Related-PROD: PROD-35812
Change-Id: Ib1b49de8ae148b22440e5701ecb6ade31d00a77b
diff --git a/docker/swarm/stack/monitoring/alerta.yml b/docker/swarm/stack/monitoring/alerta.yml
index ac16a2b..0470a09 100644
--- a/docker/swarm/stack/monitoring/alerta.yml
+++ b/docker/swarm/stack/monitoring/alerta.yml
@@ -29,6 +29,7 @@
               environment:
                 ADMIN_USERS: ${_param:alerta_admin_username}
                 ADMIN_PASSWORD_FILE: "/run/secrets/alerta"
+                AUTH_REQUIRED: "True"
                 MONGO_URI: ${_param:alerta_mongodb_uri}
                 PLUGINS: ""
               secrets: