Now forums can enroll their sites to be showcased in the Discourse [Discover](https://discourse.org/discover) directory. Once they enable the site setting `include_in_discourse_discover` to enroll their forum the `CallDiscourseHub` job will ping the `api.discourse.org/api/discover/enroll` endpoint. Then the Discourse Hub will fetch the basic details from the forum and add it to the review queue. If the site is approved then the forum details will be displayed in the `/discover` page.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
