Fix ChatOps Slack responder for gitlab.com

The responder method can only exist on a Service model subclass

ee/app/models/project_services/gitlab_slack_application_service.rb

@@ -40,4 +40,8 @@ class GitlabSlackApplicationService < Service
   def fields
     []
   end
+
+  def chat_responder
+    Gitlab::Chat::Responder::Slack
+  end
 end

ee/app/services/projects/slack_application_install_service.rb

@@ -30,10 +30,6 @@ module Projects
       success
     end
 
-    def chat_responder
-      Gitlab::Chat::Responder::Slack
-    end
-
     private
 
     # rubocop: disable CodeReuse/ActiveRecord

ee/changelogs/unreleased/fix_chatops_responder.yml

+---
+title: Fix ChatOps Slack responder for gitlab.com
+merge_request: 10416
+author:
+type: fixed

ee/spec/models/project_services/gitlab_slack_application_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe GitlabSlackApplicationService do
+  describe '#chat_responder' do
+    it 'returns the chat responder to use' do
+      expect(subject.chat_responder).to eq(Gitlab::Chat::Responder::Slack)
+    end
+  end
+end

ee/spec/services/projects/slack_application_install_service_spec.rb

@@ -46,12 +46,4 @@ describe Projects::SlackApplicationInstallService do
     expect_slack_integration_is_created(project)
     expect_chat_name_is_created(project)
   end
-
-  describe '#chat_responder' do
-    it 'returns the chat responder to use' do
-      srv = service
-
-      expect(srv.chat_responder).to eq(Gitlab::Chat::Responder::Slack)
-    end
-  end
 end