Include the user_id in user_*_team system hooks.

This fixes an issue where the user_id is not included in the data for
user_add_to_team and user_remove_from_team system hooks.  The documentation
already states that the user_id should be included.

app/services/system_hooks_service.rb

@@ -101,6 +101,7 @@ class SystemHooksService
       project_id: model.project.id,
       user_name: model.user.name,
       user_email: model.user.email,
+      user_id: model.user.id,
       access_level: model.human_access,
       project_visibility: Project.visibility_levels.key(model.project.visibility_level_field).downcase
     }

spec/services/system_hooks_service_spec.rb

@@ -13,8 +13,8 @@ describe SystemHooksService, services: true do
     it { expect(event_data(user, :destroy)).to include(:event_name, :name, :created_at, :updated_at, :email, :user_id) }
     it { expect(event_data(project, :create)).to include(:event_name, :name, :created_at, :updated_at, :path, :project_id, :owner_name, :owner_email, :project_visibility) }
     it { expect(event_data(project, :destroy)).to include(:event_name, :name, :created_at, :updated_at, :path, :project_id, :owner_name, :owner_email, :project_visibility) }
-    it { expect(event_data(project_member, :create)).to include(:event_name, :created_at, :updated_at, :project_name, :project_path, :project_path_with_namespace, :project_id, :user_name, :user_email, :access_level, :project_visibility) }
-    it { expect(event_data(project_member, :destroy)).to include(:event_name, :created_at, :updated_at, :project_name, :project_path, :project_path_with_namespace, :project_id, :user_name, :user_email, :access_level, :project_visibility) }
+    it { expect(event_data(project_member, :create)).to include(:event_name, :created_at, :updated_at, :project_name, :project_path, :project_path_with_namespace, :project_id, :user_name, :user_email, :user_id, :access_level, :project_visibility) }
+    it { expect(event_data(project_member, :destroy)).to include(:event_name, :created_at, :updated_at, :project_name, :project_path, :project_path_with_namespace, :project_id, :user_name, :user_email, :user_id, :access_level, :project_visibility) }
     it { expect(event_data(key, :create)).to include(:username, :key, :id) }
     it { expect(event_data(key, :destroy)).to include(:username, :key, :id) }