Let all mutating flows accept metadata extension

This is so we can associate history records with all mutations when doing
database maintenance.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123209304

java/google/registry/flows/ResourceCreateOrMutateFlow.java

@@ -48,6 +48,7 @@ public abstract class ResourceCreateOrMutateFlow
 
   @Override
   protected final void initSingleResourceFlow() throws EppException {
+    registerExtensions(MetadataExtension.class);
     metadataExtension = eppInput.getSingleExtension(MetadataExtension.class);
     initRepoId();
     initHistoryEntry();