RestApiServlet: Add AcceptsDelete direct on collection resource

In some rare cases we need to accept delete direct on collection
resource. One use case is delete change edit:

  DELETE /changes/<id>/edit

Note that change edit is itself a collection resource.

Change-Id: Ib3b99e91d1729e7d9a30d0fc939f531f1bf75238

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/AcceptsDelete.java

@@ -0,0 +1,35 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// 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 com.google.gerrit.extensions.restapi;
+
+
+/**
+ * Optional interface for {@link RestCollection}.
+ * <p>
+ * Collections that implement this interface can accept a {@code DELETE} directly
+ * on the collection itself.
+ */
+public interface AcceptsDelete<P extends RestResource> {
+  /**
+   * Handle deletion of a child resource by DELETE on the collection.
+   *
+   * @param parent parent collection handle.
+   * @param id id of the resource being created (optional).
+   * @return a view to perform the deletion.
+   * @throws RestApiException the view cannot be constructed.
+   */
+  <I> RestModifyView<P, I> delete(P parent, IdString id)
+      throws RestApiException;
+}