Fix error when reordering/deleting subgroup epics

ee/app/serializers/linked_epic_entity.rb

@@ -14,6 +14,6 @@ class LinkedEpicEntity < Grape::Entity
   end
 
   expose :relation_path do |epic|
-    group_epic_link_path(epic.group, request.issuable.iid, epic.id)
+    group_epic_link_path(request.issuable.group, request.issuable.iid, epic.id)
   end
 end

ee/changelogs/unreleased/weimeng-fix-subgroup-epics.yml

+---
+title: Fix error when reordering/deleting subgroup epics
+merge_request: 11837
+author:
+type: fixed

ee/spec/services/epic_links/list_service_spec.rb

@@ -18,7 +18,7 @@ describe EpicLinks::ListService, :postgresql do
         state: epic.state,
         reference: epic.to_reference(group),
         path: "/groups/#{epic.group.full_path}/-/epics/#{epic.iid}",
-        relation_path: "/groups/#{epic.group.full_path}/-/epics/#{parent_epic.iid}/links/#{epic.id}"
+        relation_path: "/groups/#{parent_epic.group.full_path}/-/epics/#{parent_epic.iid}/links/#{epic.id}"
       }
     end
   end