Add support of default fields of a generic alert

The parser looks for the list of fields to paste them
in an issue's summary:

* start_time
* description
* monitoring_tool
* service
* hosts

If any of the fields are not present, they will be excluded.

If the title field is missing
the parser will set the field to the default value.

ee/lib/gitlab/alerting/notification_payload_parser.rb

@@ -3,6 +3,8 @@
 module Gitlab
   module Alerting
     class NotificationPayloadParser
+      DEFAULT_TITLE = 'New: Incident'
+
       def initialize(payload)
         @payload = payload.to_h.with_indifferent_access
       end
@@ -13,16 +15,32 @@ module Gitlab
 
       def call
         {
-          'annotations' => {
-            'title' => payload[:title]
-          },
-          'startsAt' => payload[:starts_at]
-        }
+          'annotations' => annotations,
+          'startsAt' => payload[:start_time]
+        }.compact
       end
 
       private
 
       attr_reader :payload
+
+      def title
+        payload[:title].presence || DEFAULT_TITLE
+      end
+
+      def annotations
+        {
+          'title' => title,
+          'description' => payload[:description],
+          'monitoring_tool' => payload[:monitoring_tool],
+          'service' => payload[:service],
+          'hosts' => hosts
+        }.compact
+      end
+
+      def hosts
+        payload[:hosts] && Array(payload[:hosts])
+      end
     end
   end
 end

ee/spec/lib/gitlab/alerting/notification_payload_parser_spec.rb

@@ -10,7 +10,11 @@ describe Gitlab::Alerting::NotificationPayloadParser do
     let(:payload) do
       {
         'title' => 'alert title',
-        'starts_at' => starts_at.rfc3339
+        'start_time' => starts_at.rfc3339,
+        'description' => 'Description',
+        'monitoring_tool' => 'Monitoring tool name',
+        'service' => 'Service',
+        'hosts' => ['gitlab.com']
       }
     end
 
@@ -18,11 +22,45 @@ describe Gitlab::Alerting::NotificationPayloadParser do
       is_expected.to eq(
         {
           'annotations' => {
-            'title' => 'alert title'
+            'title' => 'alert title',
+            'description' => 'Description',
+            'monitoring_tool' => 'Monitoring tool name',
+            'service' => 'Service',
+            'hosts' => ['gitlab.com']
           },
           'startsAt' => starts_at.rfc3339
         }
       )
     end
+
+    context 'when title is blank' do
+      before do
+        payload[:title] = ''
+      end
+
+      it 'sets a predefined title' do
+        expect(subject['annotations']['title']).to eq('New: Incident')
+      end
+    end
+
+    context 'when hosts attribute is a string' do
+      before do
+        payload[:hosts] = 'gitlab.com'
+      end
+
+      it 'returns hosts as an array of one element' do
+        expect(subject['annotations']['hosts']).to eq(['gitlab.com'])
+      end
+    end
+
+    context 'when payload is blank' do
+      let(:payload) { {} }
+
+      it 'returns only default title' do
+        is_expected.to eq(
+          'annotations' => { 'title' => 'New: Incident' }
+        )
+      end
+    end
   end
 end

ee/spec/services/projects/alerting/notify_service_spec.rb

@@ -18,7 +18,7 @@ describe Projects::Alerting::NotifyService do
     let(:payload_raw) do
       {
         'title' => 'alert title',
-        'starts_at' => starts_at.rfc3339
+        'start_time' => starts_at.rfc3339
       }
     end
     let(:payload) { ActionController::Parameters.new(payload_raw).permit! }