services: cuirass: Honor 'user' and 'group'.

* gnu/services/cuirass.scm (cuirass-shepherd-service): Pass the user and
group of CONFIG to 'make-forkexec-constructor'.

gnu/services/cuirass.scm

@@ -67,6 +67,8 @@ (define (cuirass-shepherd-service config)
    (cuirass-configuration? config)
    (let ((cache-directory  (cuirass-configuration-cache-directory config))
          (log-file         (cuirass-configuration-log-file config))
+         (user             (cuirass-configuration-user config))
+         (group            (cuirass-configuration-group config))
          (interval         (cuirass-configuration-interval config))
          (database         (cuirass-configuration-database config))
          (specs            (cuirass-configuration-specifications config))
@@ -90,6 +92,8 @@ (define (cuirass-shepherd-service config)
                             "--interval" #$(number->string interval)
                             #$@(if use-substitutes? '("--use-substitutes") '())
                             #$@(if one-shot? '("--one-shot") '()))
+                      #:user #$user
+                      #:group #$group
                       #:log-file #$log-file))
             (stop #~(make-kill-destructor)))))))