Add ability to delete a serverless domain

- Create route for destroy
- Create destroy action

app/controllers/admin/serverless/domains_controller.rb

@@ -2,7 +2,7 @@
 
 class Admin::Serverless::DomainsController < Admin::ApplicationController
   before_action :check_feature_flag
-  before_action :domain, only: [:update, :verify]
+  before_action :domain, only: [:update, :verify, :destroy]
 
   def index
     @domain = PagesDomain.instance_serverless.first_or_initialize
@@ -30,6 +30,14 @@ class Admin::Serverless::DomainsController < Admin::ApplicationController
     end
   end
 
+  def destroy
+    domain.destroy!
+
+    redirect_to admin_serverless_domains_path,
+                status: :found,
+                notice: _('Domain was successfully deleted.')
+  end
+
   def verify
     result = VerifyPagesDomainService.new(domain).execute
 

config/routes/admin.rb

@@ -33,7 +33,7 @@ namespace :admin do
   resources :gitaly_servers, only: [:index]
 
   namespace :serverless do
-    resources :domains, only: [:index, :create, :update] do
+    resources :domains, only: [:index, :create, :update, :destroy] do
       member do
         post '/verify', to: 'domains#verify'
       end

locale/gitlab.pot

@@ -6886,6 +6886,9 @@ msgstr ""
 msgid "Domain was successfully created."
 msgstr ""
 
+msgid "Domain was successfully deleted."
+msgstr ""
+
 msgid "Domain was successfully updated."
 msgstr ""
 

spec/controllers/admin/serverless/domains_controller_spec.rb

@@ -295,4 +295,62 @@ describe Admin::Serverless::DomainsController do
       end
     end
   end
+
+  describe '#destroy' do
+    let!(:domain) { create(:pages_domain, :instance_serverless) }
+
+    context 'non-admin user' do
+      before do
+        sign_in(user)
+      end
+
+      it 'responds with 404' do
+        delete :destroy, params: { id: domain.id }
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    context 'admin user' do
+      before do
+        sign_in(admin)
+      end
+
+      context 'with serverless_domain feature disabled' do
+        before do
+          stub_feature_flags(serverless_domain: false)
+        end
+
+        it 'responds with 404' do
+          delete :destroy, params: { id: domain.id }
+
+          expect(response).to have_gitlab_http_status(:not_found)
+        end
+      end
+
+      context 'when domain exists' do
+        context 'and is not associated to any clusters' do
+          it 'deletes the domain' do
+            expect { delete :destroy, params: { id: domain.id } }
+              .to change { PagesDomain.count }.from(1).to(0)
+
+            expect(response).to have_gitlab_http_status(:found)
+            expect(flash[:notice]).to include('Domain was successfully deleted.')
+          end
+        end
+      end
+
+      context 'when domain does not exist' do
+        before do
+          domain.destroy!
+        end
+
+        it 'responds with 404' do
+          delete :destroy, params: { id: domain.id }
+
+          expect(response).to have_gitlab_http_status(:not_found)
+        end
+      end
+    end
+  end
 end