How to obtain approvalid vis REST API?

Again, my company wants to build an extern web application using JIRA as the backend workflow engine.
We already started with JIRA Rest API (https://developer.atlassian.com/jiradev/jira-apis/jira-rest-apis),

Now we need to approve/reject issues (in JIRA GUI Submit/Return). We tried to use this REST call:
/rest/servicedeskapi/request/{issueIdOrKey}/approval/{approvalId}
But it requires approvalId.

We then tried this Rest call: /rest/servicedeskapi/request/{issueIdOrKey}/approval
But no approvalId in the response.

My question is: how can I obtain approvalid via REST API?

Thanks in advanced!

Hi. Same here… it’s not working, and always returning an empty “values”:
$ curl -stderr -u apiuser:*** -G http://…/rest/servicedeskapi/request/SERVICE-228/approval -H ‘X-ExperimentalApi:true’ | python3 -mjson.tool
{
“size”: 0,
“start”: 0,
“limit”: 50,
“isLastPage”: true,
“_links”: {
},
“values”: []
}

Did You find a solution? is it possible to do this with the normal Jira-Server API (Not ServiceDeskAPI)?

Thanks!