Allow blank external_dashboard_url

Allow blank external_dashboard_url on project_metrics_setting. This is
needed so we can change other fields while keeping
external_dashboard_url blank.

app/models/project_metrics_setting.rb

@@ -4,6 +4,7 @@ class ProjectMetricsSetting < ApplicationRecord
   belongs_to :project
 
   validates :external_dashboard_url,
+    allow_nil: true,
     length: { maximum: 255 },
     addressable_url: { enforce_sanitization: true, ascii_only: true }
 

app/services/projects/operations/update_service.rb

@@ -41,9 +41,9 @@ module Projects
         attribs = params[:metrics_setting_attributes]
         return {} unless attribs
 
-        destroy = attribs[:external_dashboard_url].blank?
+        attribs[:external_dashboard_url] = attribs[:external_dashboard_url].presence
 
-        { metrics_setting_attributes: attribs.merge(_destroy: destroy) }
+        { metrics_setting_attributes: attribs }
       end
 
       def error_tracking_params

spec/models/project_metrics_setting_spec.rb

@@ -44,12 +44,12 @@ describe ProjectMetricsSetting do
       it { is_expected.to be_valid }
     end
 
-    context 'external_dashboard_url is blank' do
-      before do
-        subject.external_dashboard_url = ''
-      end
+    context 'dashboard_timezone' do
+      it { is_expected.to define_enum_for(:dashboard_timezone).with_values({ local: 0, utc: 1 }) }
 
-      it { is_expected.to be_invalid }
+      it 'defaults to local' do
+        expect(subject.dashboard_timezone).to eq('local')
+      end
     end
   end
 end

spec/services/projects/operations/update_service_spec.rb

@@ -126,21 +126,23 @@ describe Projects::Operations::UpdateService do
           )
           expect(project.metrics_setting.dashboard_timezone).to eq('utc')
         end
+      end
 
-        context 'with blank external_dashboard_url in params' do
+      context 'with blank external_dashboard_url' do
         let(:params) do
           {
             metrics_setting_attributes: {
-                external_dashboard_url: ''
+              external_dashboard_url: '',
+              dashboard_timezone: 'utc'
             }
           }
         end
 
-          it 'destroys the metrics_setting entry in DB' do
+        it 'updates dashboard_timezone' do
           expect(result[:status]).to eq(:success)
 
-            expect(project.reload.metrics_setting).to be_nil
-          end
+          expect(project.reload.metrics_setting.external_dashboard_url).to be(nil)
+          expect(project.metrics_setting.dashboard_timezone).to eq('utc')
         end
       end
     end