Add a layer of safety around required ActivityPub Actor fields (#4703)

* fix(ap): add safe constructors, getters, and validators to ActivityPub actors to address #4701

* chore: replace nil check with the new Validate() method

* chore(test): added test to verify the values extracted from actors

* fix: return the specific error type + test for it

* fix(ap): add recovery for each AP inbox worker for a worst case scenario

* fix(ap): add additional safe accessor methods to other AP entities other than actors

* chore(tests): add tests for the new safe accessors

* fix(ap): handle empty public keys in AP actors

activitypub/inbox/create.go

@@ -4,10 +4,14 @@ import (
 	"context"
 
 	"github.com/go-fed/activity/streams/vocab"
+	"github.com/owncast/owncast/activitypub/apmodels"
 	"github.com/pkg/errors"
 )
 
 func handleCreateRequest(c context.Context, activity vocab.ActivityStreamsCreate) error {
-	iri := activity.GetJSONLDId().GetIRI().String()
+	iri, err := apmodels.GetIRIStringFromJSONLDIdProperty(activity.GetJSONLDId())
+	if err != nil {
+		return errors.Wrap(err, "create activity is missing IRI")
+	}
 	return errors.New("not handling create request of: " + iri)
 }