how do *key and mastodon subscribe to a relay based just on the inbox URI? anyone know off the top of their head? if you do an http GET to a relay inbox URI it gives you:
{
"@context": "https://www.w3.org/ns/activitystreams",
"id": "https://rel.re/inbox",
"totalItems": 1617332,
"type": "OrderedCollection"
}
ie., there's no obvious way of linking back to the relay actor https://rel.re/actor based on the inbox URI https://rel.re/inbox