Improve docker-compose file: admin password and volume for database

Fixes: #1169

docker-compose.yml

@@ -1,4 +1,14 @@
 # This is an example. Please change the configuration variables listed here.
+#
+# This example uses a volume to persist the sqlite database outside of the container,
+# please adapt the local path.  If you use a custom PUID and PGID, you need to create
+# the local path beforehand with the correct user/group.
+#
+# You can generate an admin password with: docker run -it --rm --entrypoint ihatemoney ihatemoney/ihatemoney:latest generate_password_hash
+# IMPORTANT: replace every dollar character in the result with a double dollar ($ -> $$)
+# To disable admin access, simply set the password to an empty string (ADMIN_PASSWORD=)
+#
+# See https://ihatemoney.readthedocs.io/en/latest/configuration.html to understand all settings.
 
 version: "3.9"
 
@@ -7,8 +17,8 @@ services:
     image: ihatemoney/ihatemoney:latest
     environment:
       - DEBUG=False
-      - ACTIVATE_ADMIN_DASHBOARD=False
       - ACTIVATE_DEMO_PROJECT=True
+      - ACTIVATE_ADMIN_DASHBOARD=False
       - ADMIN_PASSWORD=
       - ALLOW_PUBLIC_PROJECT_CREATION=True
       - BABEL_DEFAULT_TIMEZONE=UTC
@@ -30,5 +40,7 @@ services:
       - PORT=8000
       - PUID=0
       - PGID=0
+    volumes:
+      - /path/to/local/dir/for/sqlite/db:/database
     ports:
       - "8000:8000"