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
okay... so it "subscribes" (ie., follows) with the instance actor, but sends as other actors from the instance? so it's up to the relay to look at whether the Mastodon instance actor follows them, and if so, accept the Create from the other actor on that instance?