Make (most) containers run with a read-only filesystem

roles/matrix-postgres/tasks/import_postgres.yml

@@ -73,7 +73,7 @@
 
 - name: Note about Postgres importing alternative
   debug:
-    msg: >
+    msg: >-
       Importing Postgres database using the following command: `{{ matrix_postgres_import_command }}`.
       If this crashes, you can stop Postgres (`systemctl stop matrix-postgres`),
       delete its existing data (`rm -rf {{ matrix_postgres_data_path }}/*`), start it again (`systemctl start matrix-postgres`)