Fixes #3077: Empty "issues" attribute of Monitoring / HealthCheck result causes errors in Zabbix.

app/controllers/monitoring_controller.rb

@@ -168,6 +168,7 @@ curl http://localhost/api/v1/monitoring/health_check?token=XXX
       result = {
         healthy: true,
         message: 'success',
+        issues:  issues,
         token:   token,
       }
       render json: result

spec/requests/integration/monitoring_spec.rb

@@ -128,6 +128,7 @@ RSpec.describe 'Monitoring', type: :request do
 
       expect(json_response).to be_a_kind_of(Hash)
       expect(json_response['error']).to be_falsey
+      expect(json_response['issues']).to eq([])
       expect(json_response['healthy']).to eq(true)
       expect(json_response['message']).to eq('success')