Parsoid's v2 API is gratuitously different from the RESTbase API in some minor ways. These should be fixed so that mediawiki-core doesn't continue to have to do silly transformations between URL schemes and results. In order to ease migration, this should probably be done as a new Parsoid "v3" API, after which we can deprecate and remove support for Parsoid's "v1" and "v2" APIs.
Changes to make:
* the "body" parameter to the wt2html end point should be renamed "bodyOnly"
* the "wt" format should be renamed "wikitext"
* The result of the html2wt endpoint should be wikitext content (like in Parsoid's v1 API and RESTBase), not a JSON wrapper around the same.
* When `bodyOnly` is true, we should serialize the *children* of the `<body>` element, not the `<body>` element itself.
* We should consider supporting the `/transform/X/to/Y` route as an alias of the `/Y` route.
We should also consider reordering the version and the hostname, since we have:
`https://$wgServerName/api/rest_v1/page/html/{TITLE}` [VirtualRESTService]
`http://parsoid-lb.eqiad.wikimedia.org/v2/$wgServerName/html/{TITLE}` [Parsoid v2]
`http://rest.wikimedia.org/$wgServerName/v1/page/html/{TITLE}` [RESTbase v1]