remove postgres user creation from role

roles/postgres/tasks/main.yaml

@@ -4,13 +4,3 @@
       - postgresql
       - postgresql-contrib
       - python-psycopg2
-- block:
-    - postgresql_db: name={{ db_name }}
-    - postgresql_user:
-        name: "{{ db_user }}"
-        password: "{{ db_user_password }}"
-        db: "{{ db_name }}"
-        priv: ALL
-  become: true
-  become_method: su
-  become_user: postgres

roles/postgres/templates/mattermost.service.j2

@@ -0,0 +1,13 @@
+[Unit]
+Description=Mattermost
+After=network.target
+
+[Service]
+User=mattermost
+ExecStart=/opt/mattermost/bin/platform
+WorkingDirectory=/opt/mattermost
+Restart=always
+RestartSec=30
+
+[Install]
+WantedBy=multi-user.target