Set 202 status for running Vulnerability Exports

ee/changelogs/unreleased/197494-set-accepted-status-code-when-export-is-generating.yml

+---
+title: Return 202 Accepted status code when fetching incompleted Vulnerability Export
+  from API
+merge_request: 28314
+author:
+type: changed

ee/lib/api/vulnerability_exports.rb

@@ -55,7 +55,10 @@ module API
       get ':id/vulnerability_exports/:export_id' do
         authorize! :read_vulnerability_export, vulnerability_export
 
-        ::Gitlab::PollingInterval.set_api_header(self, interval: 5_000) unless vulnerability_export.completed?
+        unless vulnerability_export.completed?
+          ::Gitlab::PollingInterval.set_api_header(self, interval: 5_000)
+          status :accepted
+        end
 
         present vulnerability_export,
                 with: EE::API::Entities::VulnerabilityExport

ee/spec/requests/api/vulnerability_exports_spec.rb

@@ -105,7 +105,7 @@ describe API::VulnerabilityExports do
         it 'returns information about vulnerability export' do
           get_vulnerability_export
 
-          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to have_gitlab_http_status(:accepted)
           expect(response).to match_response_schema('public_api/v4/vulnerability_export', dir: 'ee')
           expect(json_response['id']).to eq vulnerability_export.id
         end