Improved groups creation and edition.

src/service/service.cr

@@ -684,12 +684,20 @@ class Service
 
 	def create_user_and_group!
 		Passwd.new("/etc/passwd", "/etc/group").tap do |passwd|
-			return if passwd.get_user user_name
+			if user = passwd.get_user user_name
+				group = passwd.get_group user_name
 
+				return if group.nil?
+
+				group.users = reverse_dependencies.map &.user_name
+
+				passwd.mod_group group
+			else
 				passwd.add_user user_name,
 					full_name: "Service[#{id}]"
 			end
 		end
+	end
 
 	def remove_user_and_group!
 		Passwd.new("/etc/passwd", "/etc/group").tap do |passwd|