Issue Summary

Fields with the same name are collapsed on the front-end and shown as one field but when I send this request, the randomly first duplicated field will be returned in the response payload

GET /rest/api/3/user/columns 

Steps to Reproduce

1. Create a field with the same name and field type in a few projects.
2. Open the advanced issue search page, add this field as a column. You will see that only one field is shown and it shows values for each such field in all projects.
3. Send GET /rest/api/3/user/columns, it only returns one of those collapsed fields.

Expected Results

GET /rest/api/3/user/columns should return all collapsed fields.
 

[
  { "label": "Issue Type", "value": "issuetype" },
  { "label": "Key", "value": "issuekey" },
  { "label": "Dev Team", "value": "customfield_10110" },
  { "label": "Dev Team", "value": "customfield_10111" }
]

Actual Results

It includes only randomly first duplicated field in the response body

[
  { "label": "Issue Type", "value": "issuetype" },
  { "label": "Key", "value": "issuekey" },
  { "label": "Dev Team", "value": "customfield_10110" }
]

Workaround

Get all fields on the site, compare each value and find collapsed fields manually.