RestApiModule: Support binding a RestView for resource creation

Instead of handling resource creation by implementing AcceptsCreate in
the RestCollection, add a new RestCreateView that can be bound via
RestApiModule.

This improves code readability since by reading the Module class we can
now directly see which REST collections support resource creation. In
addition we no longer need factories to create the REST view that
creates the resource.

This allows us at Google to bind a different REST view for the resource
creation internally while we still use the upstream REST collection for
parsing and listing. Without this change we would need to subclass the
upstream RestCollection and override the create method which is
error-prone.

This change adds REST tests for creating a resource on a root collection
(com.google.gerrit.acceptance.rest.account.CreateAccountIT#createAccountRestApi)
and for creating a resource on a child collection
(com.google.gerrit.acceptance.rest.account.CreateBranchIT#createBranchRestApi),
however it doesn't test resource creation via REST for all possible
resource types.

There are more things that we likely also want to replace by bindings
(AcceptsPost, AcceptsDelete, listing members). This should be done by
follow-up changes.

Change-Id: I5cd61f77aad2a59a02333b5f68b86bda6c353879
Signed-off-by: Edwin Kempin <ekempin@google.com>

java/com/google/gerrit/sshd/commands/CreateGroupCommand.java

@@ -91,7 +91,7 @@ final class CreateGroupCommand extends SshCommand {
     initialGroups.add(id);
   }
 
-  @Inject private CreateGroup.Factory createGroupFactory;
+  @Inject private CreateGroup createGroup;
 
   @Inject private GroupsCollection groups;
 
@@ -126,7 +126,8 @@ final class CreateGroupCommand extends SshCommand {
       input.ownerId = String.valueOf(ownerGroupId.get());
     }
 
-    GroupInfo group = createGroupFactory.create(groupName).apply(TopLevelResource.INSTANCE, input);
+    GroupInfo group =
+        createGroup.apply(TopLevelResource.INSTANCE, IdString.fromDecoded(groupName), input);
     return groups.parse(TopLevelResource.INSTANCE, IdString.fromUrl(group.id));
   }