Add changelog. Add more specs.

changelogs/unreleased/51747-gitlab-com-unable-to-import-a-project-that-was-just-exported.yml

+---
+title: Fix NULL pipeline import problem and pipeline user mapping issue
+merge_request: 21875
+author:
+type: fixed

spec/lib/gitlab/import_export/project.json

@@ -6154,6 +6154,7 @@
       "status": "failed",
       "started_at": null,
       "finished_at": null,
+      "user_id": 9999,
       "duration": null,
       "notes": [
         {

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -62,6 +62,10 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         expect(Ci::Pipeline.find_by_sha('sha-notes').notes).not_to be_empty
       end
 
+      it 'pipeline has the correct user ID' do
+        expect(Ci::Pipeline.find_by_sha('sha-notes').user_id).to eq(@user.id)
+      end
+
       it 'restores pipelines with missing ref' do
         expect(Ci::Pipeline.where(ref: nil)).not_to be_empty
       end