Copy filter_projects helper to V3

The helper will be modified in V4, so copy the original to V4 to keep the
current behavior in V3.

lib/api/v3/helpers.rb

@@ -14,6 +14,33 @@ module API
         authorize! access_level, merge_request
         merge_request
       end
+
+      # project helpers
+
+      def filter_projects(projects)
+        if params[:membership]
+          projects = projects.merge(current_user.authorized_projects)
+        end
+
+        if params[:owned]
+          projects = projects.merge(current_user.owned_projects)
+        end
+
+        if params[:starred]
+          projects = projects.merge(current_user.starred_projects)
+        end
+
+        if params[:search].present?
+          projects = projects.search(params[:search])
+        end
+
+        if params[:visibility].present?
+          projects = projects.search_by_visibility(params[:visibility])
+        end
+
+        projects = projects.where(archived: params[:archived])
+        projects.reorder(params[:order_by] => params[:sort])
+      end
     end
   end
 end