feat: Adds a webhook for when a user follows the stream (#4362)

* feat: Adds a webhook for when a user follow the stream

Frontend:
Adds a checkbox which renders only when social features are enabled.

Backend:
- Defines a new type for the event
- Implements the webhook including unit testing
- Fires the webhook inside the ApproveFollower handler

* Removes unnecessary Type fiels from Events struct

* refactor: renames SendUserFollowedEvent func to FediverseEngagementFollow and fixes linting errors

* fix: fixes unit test to reflect removed Type field from FediverseEngagementFollowEvent

* feat: fires webhook also when manual approvals are not required

* chore: slight cleanup

---------

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

activitypub/inbox/follow.go

@@ -10,6 +10,7 @@ import (
 	"github.com/owncast/owncast/activitypub/requests"
 	"github.com/owncast/owncast/activitypub/resolvers"
 	"github.com/owncast/owncast/core/chat/events"
+	"github.com/owncast/owncast/core/webhooks"
 	"github.com/owncast/owncast/persistence/configrepository"
 	"github.com/pkg/errors"
 
@@ -39,20 +40,19 @@ func handleFollowInboxRequest(c context.Context, activity vocab.ActivityStreamsF
 	}
 
 	localAccountName := configRepository.GetDefaultFederationUsername()
+	actorReference := activity.GetActivityStreamsActor()
+	object := activity.GetActivityStreamsObject()
+	objectIRI := object.At(0).GetIRI().String()
+	actorIRI := actorReference.At(0).GetIRI().String()
 
 	if approved {
 		if err := requests.SendFollowAccept(follow.Inbox, activity, localAccountName); err != nil {
 			log.Errorln("unable to send follow accept", err)
 			return err
 		}
+		go webhooks.SendFediverseEngagementFollowEvent(actorIRI)
 	}
 
-	// Save as an activity
-	actorReference := activity.GetActivityStreamsActor()
-	object := activity.GetActivityStreamsObject()
-	objectIRI := object.At(0).GetIRI().String()
-	actorIRI := actorReference.At(0).GetIRI().String()
-
 	// If this request is approved and we have not previously sent an action to
 	// chat due to a previous follow request, then do so.
 	hasPreviouslyhandled := true // Default so we don't send anything if it fails.