Fix saving of sort preference in group issues list

Save user sort preference from query parameters when vue_issues_list is
enabled.

app/controllers/groups_controller.rb

@@ -218,6 +218,8 @@ class GroupsController < Groups::ApplicationController
 
     @has_projects = group_projects.exists?
 
+    set_sort_order
+
     respond_to do |format|
       format.html
     end

spec/controllers/groups_controller_spec.rb

@@ -509,6 +509,14 @@ RSpec.describe GroupsController, factory_default: :keep do
         expect(assigns(:issues)).to eq([issue_1])
       end
     end
+
+    it 'saves the sort order to user preferences' do
+      stub_feature_flags(vue_issues_list: true)
+
+      get :issues, params: { id: group.to_param, sort: 'priority' }
+
+      expect(user.reload.user_preference.issues_sort).to eq('priority')
+    end
   end
 
   describe 'GET #merge_requests', :sidekiq_might_not_need_inline do