restructure mutations to be more extensible

On-behalf-of: @SAP [email protected]

Author: xrstf

internal/controller/sync/controller.go

@@ -103,7 +103,11 @@ func Create(
 	remoteDummy.SetGroupVersionKind(remoteGVK)
 
 	// create the syncer that holds the meat&potatoes of the synchronization logic
-	mutator := mutation.NewMutator(pubRes.Spec.Mutation)
+	mutator, err := mutation.NewMutator(pubRes.Spec.Mutation)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create mutator: %w", err)
+	}
+
 	syncer, err := sync.NewResourceSyncer(log, localManager.GetClient(), virtualWorkspaceCluster.GetClient(), pubRes, localCRD, mutator, stateNamespace, agentName)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create syncer: %w", err)