Create a blank PagerDuty webhook endpoint

Introduce a new endpoint which PagerDuty will use to send us
webhook notifications about incidents

app/controllers/projects/incident_management/pager_duty_incidents_controller.rb

+# frozen_string_literal: true
+
+module Projects
+  module IncidentManagement
+    class PagerDutyIncidentsController < Projects::ApplicationController
+      respond_to :json
+
+      skip_before_action :verify_authenticity_token
+      skip_before_action :project
+
+      prepend_before_action :repository, :project_without_auth
+
+      def create
+        result = ServiceResponse.success(http_status: :accepted)
+
+        unless Feature.enabled?(:pagerduty_webhook, @project)
+          result = ServiceResponse.error(message: 'Unauthorized', http_status: :unauthorized)
+        end
+
+        head result.http_status
+      end
+
+      private
+
+      def project_without_auth
+        @project ||= Project
+          .find_by_full_path("#{params[:namespace_id]}/#{params[:project_id]}")
+      end
+    end
+  end
+end

app/presenters/projects/prometheus/alert_presenter.rb

@@ -6,7 +6,7 @@ module Projects
       RESERVED_ANNOTATIONS = %w(gitlab_incident_markdown gitlab_y_label title).freeze
       GENERIC_ALERT_SUMMARY_ANNOTATIONS = %w(monitoring_tool service hosts).freeze
       MARKDOWN_LINE_BREAK = "  \n".freeze
-      INCIDENT_LABEL_NAME = IncidentManagement::CreateIncidentLabelService::LABEL_PROPERTIES[:title].freeze
+      INCIDENT_LABEL_NAME = ::IncidentManagement::CreateIncidentLabelService::LABEL_PROPERTIES[:title].freeze
       METRIC_TIME_WINDOW = 30.minutes
 
       def full_title

app/services/projects/alerting/notify_service.rb

@@ -4,7 +4,7 @@ module Projects
   module Alerting
     class NotifyService < BaseService
       include Gitlab::Utils::StrongMemoize
-      include IncidentManagement::Settings
+      include ::IncidentManagement::Settings
 
       def execute(token)
         return forbidden unless alerts_service_activated?
@@ -65,7 +65,7 @@ module Projects
       def process_incident_issues(alert)
         return if alert.issue
 
-        IncidentManagement::ProcessAlertWorker.perform_async(nil, nil, alert.id)
+        ::IncidentManagement::ProcessAlertWorker.perform_async(nil, nil, alert.id)
       end
 
       def send_alert_email

app/services/projects/prometheus/alerts/notify_service.rb

@@ -5,7 +5,7 @@ module Projects
     module Alerts
       class NotifyService < BaseService
         include Gitlab::Utils::StrongMemoize
-        include IncidentManagement::Settings
+        include ::IncidentManagement::Settings
 
         # This set of keys identifies a payload as a valid Prometheus
         # payload and thus processable by this service. See also

config/routes/project.rb

@@ -400,6 +400,8 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
 
       post 'alerts/notify', to: 'alerting/notifications#create'
 
+      post 'incident_management/pager_duty', to: 'incident_management/pager_duty_incidents#create'
+
       draw :legacy_builds
 
       resources :hooks, only: [:index, :create, :edit, :update, :destroy], constraints: { id: /\d+/ } do # rubocop: disable Cop/PutProjectRoutesUnderScope

spec/controllers/projects/incident_management/pager_duty_incidents_controller_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Projects::IncidentManagement::PagerDutyIncidentsController do
+  let_it_be(:project) { create(:project) }
+
+  describe 'POST #create' do
+    let(:payload) { { messages: [] } }
+
+    def make_request
+      post :create, params: project_params, body: payload.to_json, as: :json
+    end
+
+    context 'when pagerduty_webhook feature enabled' do
+      before do
+        stub_feature_flags(pagerduty_webhook: project)
+      end
+
+      it 'responds with 202 Accepted' do
+        make_request
+
+        expect(response).to have_gitlab_http_status(:accepted)
+      end
+    end
+
+    context 'when pagerduty_webhook feature disabled' do
+      before do
+        stub_feature_flags(pagerduty_webhook: false)
+      end
+
+      it 'responds with 401 Unauthorized' do
+        make_request
+
+        expect(response).to have_gitlab_http_status(:unauthorized)
+      end
+    end
+  end
+
+  private
+
+  def project_params(opts = {})
+    opts.reverse_merge(namespace_id: project.namespace, project_id: project)
+  end
+end