Add request/auth package to Nomulus release

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=147087621

java/google/registry/request/auth/AuthenticationMechanism.java

@@ -0,0 +1,34 @@
+// 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.request.auth;
+
+import javax.servlet.http.HttpServletRequest;
+
+/**
+ * A particular way to authenticate an HTTP request, returning an {@link AuthResult}.
+ *
+ * <p>For instance, a request could be authenticated using OAuth, via special request headers, etc.
+ */
+public interface AuthenticationMechanism {
+
+  /**
+   * Attempt to authenticate an incoming request.
+   *
+   * @param request the request to be authenticated
+   * @return the results of the authentication check; if the request could not be authenticated,
+   *     the mechanism should return AuthResult.NOT_AUTHENTICATED
+   */
+  AuthResult authenticate(HttpServletRequest request);
+}