Add and wire up the AllocationTokenExtension XML class

The extension itself isn't used for anything yet; allocation tokens can be
passed for domain creates and checks but are ignored if present. This will
be changed in a subsequent CL that adds AllocationToken entities and related
logic. Usage of this extension in any other EPP flow will throw an
UnsupportedExtensionException.

The relevant spec is https://tools.ietf.org/html/draft-gould-allocation-token-04

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=181343188

java/google/registry/model/domain/token/AllocationTokenExtension.java

@@ -0,0 +1,38 @@
+// Copyright 2017 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.model.domain.token;
+
+import google.registry.model.ImmutableObject;
+import google.registry.model.eppinput.EppInput.CommandExtension;
+import javax.xml.bind.annotation.XmlRootElement;
+import javax.xml.bind.annotation.XmlValue;
+
+/**
+ * An allocation token extension that may be present on EPP domain commands.
+ *
+ * @see <a href="https://tools.ietf.org/html/draft-ietf-regext-allocation-token-04">the IETF
+ *     draft</a> for full details.
+ */
+@XmlRootElement(name = "allocationToken")
+public class AllocationTokenExtension extends ImmutableObject implements CommandExtension {
+
+  /** The allocation token for the command. */
+  @XmlValue
+  String allocationToken;
+
+  public String getAllocationToken() {
+    return allocationToken;
+  }
+}

java/google/registry/model/domain/token/package-info.java

@@ -0,0 +1,31 @@
+// Copyright 2017 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.
+
+@XmlSchema(
+  namespace = "urn:ietf:params:xml:ns:allocationToken-1.0",
+  xmlns =
+      @XmlNs(
+        prefix = "allocationToken",
+        namespaceURI = "urn:ietf:params:xml:ns:allocationToken-1.0"
+      ),
+  elementFormDefault = XmlNsForm.QUALIFIED
+)
+@XmlAccessorType(XmlAccessType.FIELD)
+package google.registry.model.domain.token;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlNs;
+import javax.xml.bind.annotation.XmlNsForm;
+import javax.xml.bind.annotation.XmlSchema;

java/google/registry/model/eppinput/EppInput.java

@@ -51,6 +51,7 @@ import google.registry.model.domain.secdns.SecDnsCreateExtension;
 import google.registry.model.domain.secdns.SecDnsUpdateExtension;
 import google.registry.model.domain.superuser.DomainDeleteSuperuserExtension;
 import google.registry.model.domain.superuser.DomainTransferRequestSuperuserExtension;
+import google.registry.model.domain.token.AllocationTokenExtension;
 import google.registry.model.eppinput.ResourceCommand.ResourceCheck;
 import google.registry.model.eppinput.ResourceCommand.SingleResourceCommand;
 import google.registry.model.host.HostCommand;
@@ -329,6 +330,8 @@ public class EppInput extends ImmutableObject {
     @XmlElementRefs({
         // allocate create extension
         @XmlElementRef(type = AllocateCreateExtension.class),
+        // allocation token extension
+        @XmlElementRef(type = AllocationTokenExtension.class),
         // fee extension version 0.6
         @XmlElementRef(type = FeeCheckCommandExtensionV06.class),
         @XmlElementRef(type = FeeInfoCommandExtensionV06.class),