Include type to notes import / export

changelogs/unreleased/49517-fix-notes-import-export.yml

+---
+title: Fix diff notes and discussion notes being exported as regular notes
+merge_request: 28401
+author:
+type: fixed

lib/gitlab/import_export/import_export.yml

@@ -176,6 +176,8 @@ excluded_attributes:
     - :enabled
 
 methods:
+  notes:
+    - :type
   labels:
     - :type
   label:

spec/lib/gitlab/import_export/project_tree_saver_spec.rb

@@ -91,7 +91,10 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
       end
 
       it 'has issue comments' do
-        expect(saved_project_json['issues'].first['notes']).not_to be_empty
+        notes = saved_project_json['issues'].first['notes']
+
+        expect(notes).not_to be_empty
+        expect(notes.first['type']).to eq('DiscussionNote')
       end
 
       it 'has issue assignees' do
@@ -299,7 +302,7 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
     create(:commit_status, project: project, pipeline: ci_build.pipeline)
 
     create(:milestone, project: project)
-    create(:note, noteable: issue, project: project)
+    create(:discussion_note, noteable: issue, project: project)
     create(:note, noteable: merge_request, project: project)
     create(:note, noteable: snippet, project: project)
     create(:note_on_commit,