Add shared inbox support for ActivityPub delivery (#4755)

* feat(ap): add support for shared inboxes to reduce outbound load

* feat(db): refactor ap followers db into followers repository

* fix(ap): use the updated activity library to pull out the shared inbox endpoint

* chore(deps): point at updated build of owncast/activity

* fix(ap): typeless endpoints

* feat(test): update ActivityPub test to support shared inboxes

* chore(test): remove unused variable

* fix: feedback from review. Guard against SSRF/non-HTTPS/local and handle transaction errors

webserver/handlers/followers.go

@@ -3,13 +3,14 @@ package handlers
 import (
 	"net/http"
 
-	"github.com/owncast/owncast/activitypub/persistence"
+	"github.com/owncast/owncast/activitypub/persistence/followersrepository"
 	webutils "github.com/owncast/owncast/webserver/utils"
 )
 
 // GetFollowers will handle an API request to fetch the list of followers (non-activitypub response).
 func GetFollowers(offset int, limit int, w http.ResponseWriter, r *http.Request) {
-	followers, total, err := persistence.GetFederationFollowers(limit, offset)
+	followersRepo := followersrepository.Get()
+	followers, total, err := followersRepo.GetFollowers(limit, offset)
 	if err != nil {
 		webutils.WriteSimpleResponse(w, false, "unable to fetch followers")
 		return