Backwards compatible active_users param

The active_users param was added to SyncSeatLinkRequestWorker without an
optional nil value, which could break existing jobs.

ee/app/workers/sync_seat_link_request_worker.rb

@@ -12,7 +12,10 @@ class SyncSeatLinkRequestWorker
 
   RequestError = Class.new(StandardError)
 
-  def perform(date, license_key, max_historical_user_count, active_users)
+  # active_users param is optional as it was added in a patch release for %12.9.
+  # The optional nil value can be removed in the next major release, %13.0, when
+  # it becomes mandatory.
+  def perform(date, license_key, max_historical_user_count, active_users = nil)
     response = Gitlab::HTTP.post(
       URI_PATH,
       base_uri: EE::SUBSCRIPTIONS_URL,

ee/changelogs/unreleased/ta-fix-sync-seat-link-worker-parameter.yml

+---
+title: Allow active_users param to be optional for SyncSeatLinkRequestWorker#perform
+merge_request: 28241
+author:
+type: fixed

ee/spec/workers/sync_seat_link_request_worker_spec.rb

@@ -26,6 +26,7 @@ describe SyncSeatLinkRequestWorker, type: :worker do
       )
     end
 
+    shared_examples 'unsuccessful request' do
       context 'when the request is not successful' do
         before do
           stub_request(:post, seat_link_url)
@@ -40,4 +41,31 @@ describe SyncSeatLinkRequestWorker, type: :worker do
         end
       end
     end
+
+    it_behaves_like 'unsuccessful request'
+
+    context 'when the active_users param is not passed' do
+      subject do
+        described_class.new.perform('2020-01-01', '123', 5)
+      end
+
+      it 'still processes the job and sends a request with active_users set to nil' do
+        stub_request(:post, seat_link_url).to_return(status: 200)
+
+        subject
+
+        expect(WebMock).to have_requested(:post, seat_link_url).with(
+          headers: { 'Content-Type' => 'application/json' },
+          body: {
+            date: '2020-01-01',
+            license_key: '123',
+            max_historical_user_count: 5,
+            active_users: nil
+          }.to_json
+        )
+      end
+
+      it_behaves_like 'unsuccessful request'
+    end
+  end
 end