Merge branch '37091-create-new-epic-option-fails-on-epics-at-the-sub-group-level' into 'master'

Encoded groupId so project path works

See merge request gitlab-org/gitlab!20646

ee/app/assets/javascripts/api.js

@@ -49,7 +49,7 @@ export default {
 
   createChildEpic({ groupId, parentEpicIid, title }) {
     const url = Api.buildUrl(this.childEpicPath)
-      .replace(':id', groupId)
+      .replace(':id', encodeURIComponent(groupId))
       .replace(':epic_iid', parentEpicIid);
 
     return axios.post(url, {