The automatic generation of webrevs is currently required when using the mlbridge bot for a repository. While this feature makes sense for OpenJDK repositories, where mailing list reviews have a strong history, there are definitely projects where generating and storing webrevs is just a waste of resources.

The webrev configuration currently looks like this:

        "webrevs": {
          "html": true,
          "json": false
        },

The html element is assumed 'true' if not set while json is assumed 'false'. If both are explicitly set to false, the bot starts throwing errors.

I would like to change this to be completely opt-in. If no webrev field is set, no webrevs should be generated or linked to.