Add mattermost-exporter to mattermost docker network

pica-mattermost/docker-compose.yml

@@ -58,6 +58,8 @@ services:
     volumes:
       - /etc/localtime:/etc/localtime:ro
     env_file: ./secrets/mattermost-exporter.secrets
+    networks:
+      - mattermost
     labels:
       traefik.http.routers.mattermost-metrics.entrypoints: websecure
       traefik.http.routers.mattermost-metrics.rule: "Host(`team.picasoft.net`) && PathPrefix(`/metrics`)"