Allow multiple modified JSON files to be created/hosted

[jack-webb]

Once a file has been modified, it should be hosted on a new endpoint, so it can be used even after other modifications are made. These could be temporary, like a gist or pastebin but for our config.

They would need to show in the UI too, maybe as a modification history, probably bottom-right. Not sure what the preview for this would look like, but would need copy URL and delete as a minimum.