Support `/client/features` Unleash endpoint

ee/changelogs/unreleased/unleash-use-client-features.yml

+---
+title: Support `/client/features` Unleash endpoint
+merge_request:
+author:
+type: fixed

ee/lib/api/unleash.rb

@@ -19,10 +19,16 @@ module API
             status :ok
           end
 
+          desc 'Get a list of features (deprecated, v2 client support)'
           get 'features' do
             present project, with: ::EE::API::Entities::UnleashFeatures
           end
 
+          desc 'Get a list of features'
+          get 'client/features' do
+            present project, with: ::EE::API::Entities::UnleashFeatures
+          end
+
           post 'client/register' do
             # not supported yet
             status :ok

ee/spec/requests/api/unleash_spec.rb

@@ -66,7 +66,10 @@ describe API::Unleash do
     end
   end
 
-  describe 'GET /feature_flags/unleash/:project_id/features' do
+  %w(/feature_flags/unleash/:project_id/features /feature_flags/unleash/:project_id/client/features).each do |features_endpoint|
+    describe "GET #{features_endpoint}" do
+      let(:features_url) { features_endpoint.sub(':project_id', project_id) }
+
       subject { get api("/feature_flags/unleash/#{project_id}/features"), params, headers }
 
       it_behaves_like 'authenticated request'
@@ -94,6 +97,7 @@ describe API::Unleash do
         end
       end
     end
+  end
 
   describe 'POST /feature_flags/unleash/:project_id/client/register' do
     subject { post api("/feature_flags/unleash/#{project_id}/client/register"), params, headers }