Add extensible custom logic to the domain check flow

This also fixes up a hook on the domain create flow custom logic to use a single
parameter, which is the general pattern we want to use going forward. It also
establishes a pattern for custom logic being able to add extensions.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=139362230

java/google/registry/flows/custom/DomainCheckFlowCustomLogic.java

@@ -0,0 +1,157 @@
+// 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 com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.net.InternetDomainName;
+import google.registry.flows.EppException;
+import google.registry.flows.SessionMetadata;
+import google.registry.flows.domain.DomainCheckFlow;
+import google.registry.model.ImmutableObject;
+import google.registry.model.eppinput.EppInput;
+import google.registry.model.eppoutput.CheckData.DomainCheck;
+import google.registry.model.eppoutput.EppResponse.ResponseExtension;
+import org.joda.time.DateTime;
+
+/**
+ * A no-op base class for {@link DomainCheckFlow} custom logic.
+ *
+ * <p>Extend this class and override the hook(s) to perform custom logic.
+ */
+public class DomainCheckFlowCustomLogic extends BaseFlowCustomLogic {
+
+  protected DomainCheckFlowCustomLogic(EppInput eppInput, SessionMetadata sessionMetadata) {
+    super(eppInput, sessionMetadata);
+  }
+
+  /**
+   * A hook that runs before any validation. This is useful to e.g. add allowable extensions.
+   */
+  @SuppressWarnings("unused")
+  public void beforeValidation() throws EppException {
+    // Do nothing.
+  }
+
+  /** A hook that runs at the end of the validation step to perform additional validation. */
+  @SuppressWarnings("unused")
+  public void afterValidation(AfterValidationParameters parameters) throws EppException {
+    // Do nothing.
+  }
+
+  /**
+   * A hook that runs before the response is returned.
+   *
+   * <p>This takes the {@link DomainCheck}s and {@link ResponseExtension}s as input and returns
+   * them, potentially with modifications.
+   */
+  @SuppressWarnings("unused")
+  public BeforeResponseReturnData beforeResponse(BeforeResponseParameters parameters)
+      throws EppException {
+    return BeforeResponseReturnData.newBuilder()
+        .setDomainChecks(parameters.domainChecks())
+        .setResponseExtensions(parameters.responseExtensions())
+        .build();
+  }
+
+  /** A class to encapsulate parameters for a call to {@link #afterValidation}. */
+  @AutoValue
+  public abstract static class AfterValidationParameters extends ImmutableObject {
+
+    public abstract ImmutableMap<String, InternetDomainName> domainNames();
+
+    /**
+     * The time to perform the domain check as of. This defaults to the current time, but can be
+     * overridden in v>=0.12 of the fee extension.
+     */
+    public abstract DateTime asOfDate();
+
+    public static Builder newBuilder() {
+      return new AutoValue_DomainCheckFlowCustomLogic_AfterValidationParameters.Builder();
+    }
+
+    /** Builder for {@link AfterValidationParameters}. */
+    @AutoValue.Builder
+    public abstract static class Builder {
+
+      public abstract Builder setDomainNames(ImmutableMap<String, InternetDomainName> domainNames);
+
+      public abstract Builder setAsOfDate(DateTime asOfDate);
+
+      public abstract AfterValidationParameters build();
+    }
+  }
+
+  /** A class to encapsulate parameters for a call to {@link #beforeResponse}. */
+  @AutoValue
+  public abstract static class BeforeResponseParameters extends ImmutableObject {
+
+    public abstract ImmutableList<DomainCheck> domainChecks();
+
+    public abstract ImmutableList<? extends ResponseExtension> responseExtensions();
+
+    /**
+     * The time to perform the domain check as of. This defaults to the current time, but can be
+     * overridden in v>=0.12 of the fee extension.
+     */
+    public abstract DateTime asOfDate();
+
+    public static Builder newBuilder() {
+      return new AutoValue_DomainCheckFlowCustomLogic_BeforeResponseParameters.Builder();
+    }
+
+    /** Builder for {@link BeforeResponseParameters}. */
+    @AutoValue.Builder
+    public abstract static class Builder {
+
+      public abstract Builder setDomainChecks(ImmutableList<DomainCheck> domainChecks);
+
+      public abstract Builder setResponseExtensions(
+          ImmutableList<? extends ResponseExtension> responseExtensions);
+
+      public abstract Builder setAsOfDate(DateTime asOfDate);
+
+      public abstract BeforeResponseParameters build();
+    }
+  }
+
+  /**
+   * A class to encapsulate parameters for the return values from a call to {@link #beforeResponse}.
+   */
+  @AutoValue
+  public abstract static class BeforeResponseReturnData extends ImmutableObject {
+
+    public abstract ImmutableList<DomainCheck> domainChecks();
+
+    public abstract ImmutableList<? extends ResponseExtension> responseExtensions();
+
+    public static Builder newBuilder() {
+      return new AutoValue_DomainCheckFlowCustomLogic_BeforeResponseReturnData.Builder();
+    }
+
+    /** Builder for {@link BeforeResponseReturnData}. */
+    @AutoValue.Builder
+    public abstract static class Builder {
+
+      public abstract Builder setDomainChecks(ImmutableList<DomainCheck> domainChecks);
+
+      public abstract Builder setResponseExtensions(
+          ImmutableList<? extends ResponseExtension> responseExtensions);
+
+      public abstract BeforeResponseReturnData build();
+    }
+  }
+}