Advertise any other protocol in the discovery endpoint

[glpatcern]

This is a proposal in order to standardize how to show additional protocols in the discovery endpoint.

I'm not sure it can be espressed in OpenAPI 2.0. One more reason to convert to OpenAPI 3.0?

Edit: I fixed the PR (still with OpenAPI 2.0) so to allow to specify <any name> : "<url>", similar to how Nextcloud advertises their talk protocol:

      "protocols": {
        "talk-v1": "/ocs/v2.php/apps/spreed/api/"
      }

And the included example is deliberately inspired to the above.

@ArtificialOwl this makes Nextcloud's discovery fully standard ;-)

[glpatcern]

For reference, this is the discovery endpoint of Nextcloud:

https://cloud.nextcloud.com/ocm-provider