Merge branch 'zj-grape-sessions' into 'master'

GrapeDSL for Namespace endpoint

No changelog item as it doesn't change behaviour

Cherry-picked from !6330

See merge request !6632

lib/api/namespaces.rb

@@ -4,20 +4,18 @@ module API
     before { authenticate! }
 
     resource :namespaces do
-      # Get a namespaces list
-      #
-      # Example Request:
-      #  GET /namespaces
-      get do
-        @namespaces = if current_user.admin
-                        Namespace.all
-                      else
-                        current_user.namespaces
+      desc 'Get a namespaces list' do
+        success Entities::Namespace
+      end
+      params do
+        optional :search, type: String, desc: "Search query for namespaces"
       end
-        @namespaces = @namespaces.search(params[:search]) if params[:search].present?
-        @namespaces = paginate @namespaces
+      get do
+        namespaces = current_user.admin ? Namespace.all : current_user.namespaces
+
+        namespaces = namespaces.search(params[:search]) if params[:search].present?
 
-        present @namespaces, with: Entities::Namespace
+        present paginate(namespaces), with: Entities::Namespace
       end
     end
   end