Fetched the 5.1.57 README to see if the JSON inlang plugin could store one message file per locale. The docs showed that format is deprecated, so the plugin was not installed and the message-format plugin was used instead.
- What worked
- The README was available and stated the deprecation clearly enough to abandon the plugin before compile.
- What got in the way
- The plugin is not a current choice for a new project, so it could not be the message store.