Execute web hooks for WikiPage delete operation

* Add a new DestroyService for Wiki Pages
* Alter WikiPagesController to use the new service

app/controllers/projects/wikis_controller.rb

@@ -84,7 +84,7 @@ class Projects::WikisController < Projects::ApplicationController
 
   def destroy
     @page = @project_wiki.find_page(params[:id])
-    @page&.delete
+    WikiPages::DestroyService.new(@project, current_user).execute(@page)
 
     redirect_to(
       namespace_project_wiki_path(@project.namespace, @project, :home),

app/services/wiki_pages/destroy_service.rb

+module WikiPages
+  class DestroyService < WikiPages::BaseService
+    def execute(page)
+      if page&.delete
+        execute_hooks(page, 'delete')
+      end
+
+      page
+    end
+  end
+end

changelogs/unreleased/19302-wiki-page-delete-does-not-trigger-the-webhook.yml

+---
+title: Execute web hooks for WikiPage delete operation
+merge_request: 8198
+author:

doc/user/project/integrations/webhooks.md

@@ -714,7 +714,7 @@ X-Gitlab-Event: Merge Request Hook
 
 ### Wiki Page events
 
-Triggered when a wiki page is created or edited.
+Triggered when a wiki page is created, edited or deleted.
 
 **Request Header**:
 

spec/services/wiki_pages/destroy_service_spec.rb

+require 'spec_helper'
+
+describe WikiPages::DestroyService, services: true do
+  let(:project) { create(:empty_project) }
+  let(:user) { create(:user) }
+  let(:wiki_page) { create(:wiki_page) }
+  let(:service) { described_class.new(project, user) }
+
+  describe '#execute' do
+    before do
+      allow(service).to receive(:execute_hooks)
+      project.add_master(user)
+    end
+
+    it 'executes webhooks' do
+      service.execute(wiki_page)
+
+      expect(service).to have_received(:execute_hooks).once.with(wiki_page, 'delete')
+    end
+  end
+end