Add extensible custom logic to the domain update flow

This also adds beforeValidation hook to DomainCreateCustomFlow.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=139828346

java/google/registry/flows/custom/CustomLogicFactory.java

@@ -45,4 +45,9 @@ public class CustomLogicFactory {
       EppInput eppInput, SessionMetadata sessionMetadata) {
     return new DomainInfoFlowCustomLogic(eppInput, sessionMetadata);
   }
+
+  public DomainUpdateFlowCustomLogic forDomainUpdateFlow(
+      EppInput eppInput, SessionMetadata sessionMetadata) {
+    return new DomainUpdateFlowCustomLogic(eppInput, sessionMetadata);
+  }
 }