Add base AllocationToken validation logic for domain checks

Next up is adding custom logic so that the results of these checks can be
more meaningful.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=181660956

javatests/google/registry/flows/ResourceCheckFlowTestCase.java

@@ -31,8 +31,8 @@ public class ResourceCheckFlowTestCase<F extends Flow, R extends EppResource>
 
   protected void doCheckTest(CheckData.Check... expected) throws Exception {
     assertTransactionalFlow(false);
-    assertThat(expected).asList().containsExactlyElementsIn(
-        ((CheckData) runFlow().getResponse().getResponseData().get(0)).getChecks());
+    assertThat(((CheckData) runFlow().getResponse().getResponseData().get(0)).getChecks())
+        .containsExactlyElementsIn(expected);
     assertNoHistory();  // Checks don't create a history event.
     assertNoBillingEvents();  // Checks are always free.
   }