Document missing user group functionality
@xeruf asked in Matrix how to give an user admin privileges, and by that I noticed that we don't have the missing functionality properly documented in https://docs.stackspin.net/en/v0.8/manage_stackspin.html#users
Also document the python -m stackspin CLUSTERNAME secrets
cmd to reveal the needed admin creds for each app as workaround until we implement proper privilege management
Edited by Varac