Set-IcingaAgentServiceUser fails for parameter -user with format user@domain

[K0nne]

Set-IcingaAgentServiceUser fails if the user is defined in the format user@domain, which is a valid format.
In this case the prefix '.\' is added, which breaks the service:

Expected Behavior

Set-IcingaAgentServiceUser -User user@domain -SetPermission
[..]
[Notice]: Service User "user@domain" for service "icinga2" successfully updated

Current Behavior

The '.\'-Prefix is wrong in this case.

Set-IcingaAgentServiceUser -User user@domain -SetPermission
[..]
[Notice]: Service User ".\user@domain" for service "icinga2" successfully updated

Possible Solution

Dont add the prefix '.\' in case of the format user@domain.

Context

Your Environment

Framework: 1.10.1
PS: 5.1

[LordHepipud]

icinga> Set-IcingaServiceUser -User 'NT Authority\NetworkService'
[Notice]: Service User "NT Authority\NetworkService" for service "icinga2" successfully updated

icinga> Set-IcingaServiceUser -User 'NetworkService@NT Authority'
[Notice]: Service User "NT Authority\NetworkService" for service "icinga2" successfully updated