Allow billing plans to be mounted into the Docker container if needed

server/compose.yaml

@@ -17,6 +17,7 @@ services:
       - custom-logs:/var/logs
       - ./museum.yaml:/museum.yaml:ro
       - ./scripts/compose/credentials.yaml:/credentials.yaml:ro
+      - ./data:/data:ro
     networks:
       - internal
 

web/apps/payments/README.md

@@ -76,6 +76,9 @@ stripe:
         cancel: ?status=fail&reason=canceled
 ```
 
+Make sure you have test plans available for museum to use, by placing them in
+(say) `server/data/billing/us-testing.json`.
+
 Finally, start museum, for example:
 
 ```