Add support for creating/destroy published incidents

ee/app/models/status_page/published_incident.rb

 # frozen_string_literal: true
 
 module StatusPage
-  # Corresponds to an issue which has been published to a
-  # status-page app's AWS bucket.
+  # Corresponds to an issue which has been published to the Status Page.
   class PublishedIncident < ApplicationRecord
     self.table_name = "status_page_published_incidents"
 
     belongs_to :issue, inverse_of: :status_page_published_incident
     validates :issue, presence: true
+
+    def self.track(issue)
+      safe_find_or_create_by(issue: issue)
+    end
+
+    def self.untrack(issue)
+      find_by(issue: issue)&.destroy
+    end
   end
 end

ee/spec/models/status_page/published_incident_spec.rb

@@ -10,4 +10,42 @@ describe StatusPage::PublishedIncident do
   describe 'validation' do
     it { is_expected.to validate_presence_of(:issue) }
   end
+
+  describe '.track' do
+    let_it_be(:issue) { create(:issue) }
+
+    subject { described_class.track(issue) }
+
+    it { is_expected.to be_a(described_class) }
+    specify { expect(subject.issue).to eq issue }
+    specify { expect { subject }.to change { described_class.count }.by(1) }
+
+    context 'when the incident already exists' do
+      before do
+        create(:status_page_published_incident, issue: issue)
+      end
+
+      it { is_expected.to be_a(described_class) }
+      specify { expect(subject.issue).to eq issue }
+      specify { expect { subject }.not_to change { described_class.count } }
+    end
+  end
+
+  describe '.untrack' do
+    let_it_be(:issue) { create(:issue) }
+
+    subject { described_class.untrack(issue) }
+
+    context 'when the incident is not yet tracked' do
+      specify { expect { subject }.not_to change { described_class.count } }
+    end
+
+    context 'when the incident is already tracked' do
+      before do
+        create(:status_page_published_incident, issue: issue)
+      end
+
+      specify { expect { subject }.to change { described_class.count }.by(-1) }
+    end
+  end
 end