Add saving usage_data_id from Usage Ping response

This modifies SubmitUsagePingService to save `usage_data_id` from
version-gitlab-com app to help correlate records from RawUsageData with
those stored in the versions app, as previously this was only possible
by relying on `recorded_at`.

app/services/submit_usage_ping_service.rb

@@ -35,7 +35,10 @@ class SubmitUsagePingService
 
     raise SubmissionError.new("Unsuccessful response code: #{response.code}") unless response.success?
 
-    raw_usage_data.update_sent_at! if raw_usage_data
+    if raw_usage_data
+      raw_usage_data.update_sent_at!
+      raw_usage_data.update!(version_usage_data_id: response.dig('conv_index', 'usage_data_id'))
+    end
 
     store_metrics(response)
   end

spec/services/submit_usage_ping_service_spec.rb

@@ -46,7 +46,7 @@ RSpec.describe SubmitUsagePingService do
   end
 
   let(:with_dev_ops_score_params) { { dev_ops_score: score_params[:score] } }
-  let(:with_conv_index_params) { { conv_index: score_params[:score] } }
+  let(:with_conv_index_params) { { conv_index: score_params[:score].merge(usage_data_id: 31643) } }
   let(:without_dev_ops_score_params) { { dev_ops_score: {} } }
 
   shared_examples 'does not run' do
@@ -124,6 +124,19 @@ RSpec.describe SubmitUsagePingService do
       end
 
       it_behaves_like 'saves DevOps report data from the response'
+
+      it 'saves usage_data_id to version_usage_data_id' do
+        recorded_at = Time.current
+        usage_data = { uuid: 'uuid', recorded_at: recorded_at }
+
+        expect(Gitlab::UsageData).to receive(:data).with(force_refresh: true).and_return(usage_data)
+
+        subject.execute
+
+        raw_usage_data = RawUsageData.find_by(recorded_at: recorded_at)
+
+        expect(raw_usage_data.version_usage_data_id).to eq(31643)
+      end
     end
 
     context 'when DevOps report data is passed' do