[bug#32358] Add pcscd service

[Clément Lassieur]

Clément Lassieur <address@hidden> writes:

>> However, I don't know if Shepherd uses that PID file for anything else
>> while managing the process later on.
>
> No, it doesn't use the #:PID-FILE argument for anything else.  However,
> it does use the return value of the start procedure as a PID file to
> automatically respawn the service if it's an integer.  So you just need
> to return (call-with-input-file pid-file read) instead of #t if you want
> automatic respawning, as in
> https://git.savannah.gnu.org/cgit/guix.git/commit/?id=fdbca05d78d091bfc075e54c9fb90125262eadf0.

Note that the 'running' slot would then have the PID value, and
'make-kill-destructor' would work, so no need to change the stop
procedure.