Enable Slack Notifications for alerts

- Remove feature flag checks

app/models/alert_management/alert.rb

@@ -156,7 +156,6 @@ module AlertManagement
     end
 
     def execute_services
-      return unless Feature.enabled?(:alert_slack_event, project)
       return unless project.has_active_services?(:alert_hooks)
 
       project.execute_services(hook_data, :alert_hooks)

app/models/project_services/slack_service.rb

@@ -25,7 +25,7 @@ class SlackService < ChatNotificationService
 
   def supported_events
     additional = []
-    additional << 'alert' if Feature.enabled?(:alert_slack_event, project)
+    additional << 'alert'
 
     super + additional
   end

changelogs/unreleased/220415-feature-flag-enable-alert-slack-notifications.yml

+---
+title: Enable Slack notifications for alerts
+merge_request: 34038
+author:
+type: added

doc/user/project/integrations/slack.md

@@ -23,7 +23,23 @@ The Slack Notifications Service allows your GitLab project to send events (e.g.
 
 Your Slack team will now start receiving GitLab event notifications as configured.
 
-![Slack configuration](img/slack_configuration.png)
+### Triggers available for Slack notifications
+
+The following triggers are available for Slack notifications:
+
+- **Push**: Triggered by a push to the repository.
+- **Issue**: Triggered when an issue is created, updated, or closed.
+- **Confidential issue**: Triggered when a confidential issue is created,
+  updated, or closed.
+- **Merge request**: Triggered when a merge request is created, updated, or
+  merged.
+- **Note**: Triggered when someone adds a comment.
+- **Confidential note**: Triggered when someone adds a confidential note.
+- **Tag push**: Triggered when a new tag is pushed to the repository.
+- **Pipeline**: Triggered when a pipeline status changes.
+- **Wiki page**: Triggered when a wiki page is created or updated.
+- **Deployment**: Triggered when a deployment finishes.
+- **Alert**: Triggered when a new, unique alert is recorded.
 
 ## Troubleshooting
 

doc/user/project/operations/alert_management.md

@@ -155,3 +155,11 @@ After completing their portion of investigating or fixing the alert, users can
 unassign their account from the alert when their role is complete.
 The [alerts status](#alert-management-statuses) can be updated to
 reflect if the alert has been resolved.
+
+### Slack Notifications
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/216326) in GitLab 13.1.
+
+You can be alerted via a Slack message when a new alert has been received.
+
+See the [Slack Notifications Service docs](../integrations/slack.md) for information on how to set this up.

spec/services/alert_management/process_prometheus_alert_service_spec.rb

@@ -90,18 +90,6 @@ RSpec.describe AlertManagement::ProcessPrometheusAlertService do
 
               expect(ProjectServiceWorker).to have_received(:perform_async).with(slack_service.id, an_instance_of(Hash))
             end
-
-            context 'feature flag disabled' do
-              before do
-                stub_feature_flags(alert_slack_event: false)
-              end
-
-              it 'does not execute the alert service hooks' do
-                subject
-
-                expect(ProjectServiceWorker).not_to have_received(:perform_async)
-              end
-            end
           end
 
           context 'when alert cannot be created' do

spec/services/projects/alerting/notify_service_spec.rb

@@ -145,18 +145,6 @@ describe Projects::Alerting::NotifyService do
             expect(ProjectServiceWorker).to have_received(:perform_async).with(slack_service.id, an_instance_of(Hash))
           end
 
-          context 'feature flag disabled' do
-            before do
-              stub_feature_flags(alert_slack_event: false)
-            end
-
-            it 'does not executes the alert service hooks' do
-              subject
-
-              expect(ProjectServiceWorker).not_to have_received(:perform_async)
-            end
-          end
-
           context 'existing alert with same fingerprint' do
             let(:fingerprint_sha) { Digest::SHA1.hexdigest(fingerprint) }
             let!(:existing_alert) { create(:alert_management_alert, project: project, fingerprint: fingerprint_sha) }