bug#64862: [feature request] [shepherd] Specifying POSIX capabilities on services

[Maxim Cournoyer]

Hello,

It'd be useful to be able to specify POSIX capabilities a Shepherd
service should have, for example for an unprivileged process to be able
to bind to ports lower than 1024.

This came up while reviewing #63082, which patch 10/16 (now dropped
because of loss of functionality) suggested to let the user/group change
be effected by Shepherd instead of by MPD itself (see:
https://issues.guix.gnu.org/63082#98).

I know that NixOS has some mechanism to do that; I think it was a simple
shell script wrapper setting the capabilities, but that's all I
remember.

-- 
Thanks,
Maxim