Forbidden characters in GroupShare user name?

Hi all,

We are using a third party system, XTRF, to create users in GroupShare 2017.
The integration will fetch the existing user name in XTRF and generate an account in GroupShare with the same user name.

I wonder if there is any official documentation over which characters are allowed? 
I'm thinking of characters which typically breaks user names like <>;:/&\ etc, as well as 16-bit characters like Chinese etc.

Can anyone proved an exhaustive list?

Thanks in advance,

/Jan