I tested it from Katalon Studio, it works, but you need first to impersonate as the domain administrator for domain.tld using api/v1/settings/sysadmin/manage-domain.
So,
Step 1/ Login as system admin account and get auth token
Step 2/ Get new token to manage specific domain api/v1//settings/sysadmin/manage-domain/domain.tld
Result:
{
"tempPassword":"LUr3vf}TGZ$t=a4",
"tempPasswordExpUtc":"2019-06-23T20:55:33.7854325Z",
"success":true,
"resultCode":200,
"message":""
}
Sébastien Riccio
System & Network Admin
https://swisscenter.com