fix missing issue assignees

lib/gitlab/import_export/import_export.yml

@@ -19,6 +19,7 @@ project_tree:
     - milestone:
       - events:
         - :push_event_payload
+    - :issue_assignees
   - snippets:
     - :award_emoji
     - notes:

spec/lib/gitlab/import_export/project.json

@@ -43,7 +43,7 @@
   "issues": [
     {
       "id": 40,
-      "title": "Voluptatem amet doloribus deleniti eos maxime repudiandae molestias.",
+      "title": "Voluptatem",
       "assignee_id": 1,
       "author_id": 22,
       "project_id": 5,
@@ -70,6 +70,12 @@
         "updated_at": "2016-06-14T15:02:04.415Z",
         "state": "active",
         "iid": 1,
+        "issue_assignees": [
+          {
+            "user_id": 1,
+            "issue_id": 1
+          }
+        ]
         "events": [
           {
             "id": 487,

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -63,6 +63,10 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         expect(issue.reload.updated_at.to_s).to eq('2016-06-14 15:02:47 UTC')
       end
 
+      it 'has issue assignees' do
+        expect(project.issues.where(title: 'Voluptatem').first.issue_assignees).not_to be_empty
+      end
+
       it 'contains the merge access levels on a protected branch' do
         expect(ProtectedBranch.first.merge_access_levels).not_to be_empty
       end

spec/lib/gitlab/import_export/project_tree_saver_spec.rb

@@ -77,6 +77,10 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
         expect(saved_project_json['issues'].first['notes']).not_to be_empty
       end
 
+      it 'has issue assignees' do
+        expect(saved_project_json['issues'].first['issue_assignees']).not_to be_empty
+      end
+
       it 'has author on issue comments' do
         expect(saved_project_json['issues'].first['notes'].first['author']).not_to be_empty
       end