address activitypub notes to the streamer's follower collection (#4314)

* make a new function to generate appropriate to and cc apub objects

* use new addressing function to set "public" message addressing appropriately with the followers collection

* early return from sending federated message if federation is disabled

* cleanup old addressing code, apply new addressing mechanism to live notifications as well

* linter fix

* Update activitypub/outbox/outbox.go

---------

Co-authored-by: Gabe Kangas <gabek@real-ity.com>

webserver/handlers/admin/federation.go

@@ -16,6 +16,13 @@ func SendFederatedMessage(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	configRepository := configrepository.Get()
+
+	if !configRepository.GetFederationEnabled() {
+		webutils.WriteSimpleResponse(w, false, "Federation is disabled")
+		return
+	}
+
 	configValue, success := getValueFromRequest(w, r)
 	if !success {
 		return