services: nfs: Add verbosity control to idmap-service-type.

* gnu/services/nfs.scm (<idmap-configuration>)[verbosity]: New field.
(idmap-configuration-verbosity): New procedure.
(idmap-service-type): Use it.
* doc/guix.texi (Network File System): Document it.

doc/guix.texi

@@ -22044,6 +22044,9 @@ The local NFSv4 domain name.
 This must be a string or @code{#f}.
 If it is @code{#f} then the daemon will use the host's fully qualified domain name.
 
+@item @code{verbosity} (default: @code{0})
+The verbosity level of the daemon.
+
 @end table
 @end deftp
 

gnu/services/nfs.scm

@@ -167,7 +167,9 @@
   (domain                idmap-configuration-domain
                          (default #f))
   (nfs-utils             idmap-configuration-nfs-utils
-                         (default nfs-utils)))
+                         (default nfs-utils))
+  (verbosity             idmap-configuration-verbosity
+                         (default 0)))
 
 (define idmap-service-type
   (let ((proc
@@ -185,6 +187,10 @@
              (plain-file "idmapd.conf"
                          (string-append
                           "\n[General]\n"
+                          "Verbosity = "
+                          (number->string
+                           (idmap-configuration-verbosity config))
+                          "\n"
                           (if domain
                               (format #f "Domain = ~a\n" domain)
                               "")