ogMiddleware(ctx: Context,next: Next): Promise<unknown>
Serves index.html with the tags of the dump, user or public playlist a
path names (parsePagePath), and passes the request on when it names none
that exists or the visitor may see. A path naming one by a former name, a
user's or a slug, or in another case, gets a 301 to its current path. The
page's URL is on FRONTEND_URL and the images' on PUBLIC_URL, not on the
request's origin, which a reverse proxy may have rewritten to an internal
host or plain http.