Put dashboard gold trial behind feature flag

This is behind a flag because it's a change in behaviour from the
previous callout. We've fixed when it displays, but it might surprise
some people. So to be cautious, we allow it to be disabled entirely.

ee/app/helpers/ee/user_callouts_helper.rb

@@ -52,7 +52,8 @@ module EE
     def render_dashboard_gold_trial(user)
       return unless show_gold_trial?(user, GOLD_TRIAL) &&
           user_default_dashboard?(user) &&
-          has_no_trial_or_gold_plan?(user) &&
+          ::Feature.enabled?(:render_dashboard_gold_trial, default_enabled: true) &&
+          has_no_trial_or_paid_plan?(user) &&
           has_some_namespaces_with_no_trials?(user)
 
       render 'shared/gold_trial_callout_content'
@@ -118,7 +119,7 @@ module EE
       ::Gitlab.com? && !::Gitlab::Database.read_only?
     end
 
-    def has_no_trial_or_gold_plan?(user)
+    def has_no_trial_or_paid_plan?(user)
       return false if user.has_paid_namespace?
 
       !user.any_namespace_with_trial?

ee/spec/helpers/ee/user_callouts_helper_spec.rb

@@ -177,7 +177,7 @@ describe EE::UserCalloutsHelper do
     let_it_be(:gold_plan) { create(:gold_plan) }
     let(:user) { namespace.owner }
 
-    where(:has_some_namespaces_with_no_trials?, :show_gold_trial?, :user_default_dashboard?, :has_no_trial_or_gold_plan?, :should_render?) do
+    where(:has_some_namespaces_with_no_trials?, :show_gold_trial?, :user_default_dashboard?, :has_no_trial_or_paid_plan?, :should_render?) do
       true  | true  | true  | true  | true
       true  | true  | true  | false | false
       true  | true  | false | true  | false
@@ -202,7 +202,7 @@ describe EE::UserCalloutsHelper do
         allow(helper).to receive(:user_default_dashboard?) { user_default_dashboard? }
         allow(helper).to receive(:has_some_namespaces_with_no_trials?) { has_some_namespaces_with_no_trials? }
 
-        unless has_no_trial_or_gold_plan?
+        unless has_no_trial_or_paid_plan?
           create(:gitlab_subscription, hosted_plan: gold_plan, namespace: namespace)
         end
       end
@@ -217,6 +217,22 @@ describe EE::UserCalloutsHelper do
         helper.render_dashboard_gold_trial(user)
       end
     end
+
+    context 'when render_dashboard_gold_trial feature is disabled' do
+      before do
+        stub_feature_flags(render_dashboard_gold_trial: false)
+
+        allow(helper).to receive(:show_gold_trial?).and_return(true)
+        allow(helper).to receive(:user_default_dashboard?).and_return(true)
+        allow(helper).to receive(:has_some_namespaces_with_no_trials?).and_return(true)
+      end
+
+      it 'does not render' do
+        expect(helper).not_to receive(:render)
+
+        helper.render_dashboard_gold_trial(user)
+      end
+    end
   end
 
   describe '#render_billings_gold_trial' do