Ensure that poll messages are created in domain create flow tests

Also ensures that a custom logic hook is called on create.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=143112481

javatests/google/registry/flows/custom/TestDomainCreateFlowCustomLogic.java

@@ -0,0 +1,49 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.flows.custom;
+
+import static google.registry.model.ofy.ObjectifyService.ofy;
+
+import google.registry.flows.EppException;
+import google.registry.flows.SessionMetadata;
+import google.registry.model.eppinput.EppInput;
+import google.registry.model.poll.PollMessage;
+
+/** A class to customize {@link DomainCreateFlowCustomLogic} for testing. */
+public class TestDomainCreateFlowCustomLogic extends DomainCreateFlowCustomLogic {
+
+  protected TestDomainCreateFlowCustomLogic(EppInput eppInput, SessionMetadata sessionMetadata) {
+    super(eppInput, sessionMetadata);
+  }
+
+  @Override
+  public EntityChanges beforeSave(BeforeSaveParameters parameters) throws EppException {
+    if (parameters.newDomain().getFullyQualifiedDomainName().startsWith("custom-logic-test")) {
+      PollMessage extraPollMessage =
+          new PollMessage.OneTime.Builder()
+              .setParent(parameters.historyEntry())
+              .setEventTime(ofy().getTransactionTime())
+              .setClientId(getSessionMetadata().getClientId())
+              .setMsg("Custom logic was triggered")
+              .build();
+      return EntityChanges.newBuilder()
+          .setSaves(parameters.entityChanges().getSaves())
+          .addSave(extraPollMessage)
+          .setDeletes(parameters.entityChanges().getDeletes())
+          .build();
+    }
+    return parameters.entityChanges();
+  }
+}