gnu: greetd-service-type: Add supplementary groups to greeter.

* gnu/services/base.scm (<greetd-configuration>)
[greeter-supplementary-groups]: New field.
(%greetd-accounts): Rename to...
(greetd-accounts): ... this.  Convert to a function that takes a config
argument.  Use greeter-supplementary-groups.
(greetd-service-type): Adjust accordingly.
* gnu/tests/desktop.scm (%minimal-services): Add test for
greeter-supplementary-groups.
* doc/guix.texi ("Base Services")[greetd-service-type]: Document
greeter-supplementary-groups.

1 files changed, 7 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 0642b83923..7bce8a567c 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -18559,6 +18559,13 @@ the 'root' account has just been created.
 @item @code{terminals} (default: @code{'()})
 List of @code{greetd-terminal-configuration} per terminal for which
 @code{greetd} should be started.
+
+@item @code{greeter-supplementary-groups} (default: @code{'()})
+List of groups which should be added to @code{greeter} user. For instance:
+@lisp
+(greeter-supplementary-groups '("seat" "video"))
+@end lisp
+Note that this example will fail if @code{seat} group does not exist.
 @end table
 @end deftp