fix: add missing validation for group name

Author: kenjis

src/Commands/User.php

@@ -603,6 +603,11 @@ private function addgroup($group = null, $username = null, $email = null): void
             $group = $this->prompt('Group', null, 'required');
         }
 
+        // Validate the group
+        if (! $this->validateGroup($group)) {
+            throw new CancelException('Invalid group: "' . $group . '"');
+        }
+
         $user = $this->findUser('Add user to group', $username, $email);
 
         $confirm = $this->prompt(
@@ -635,6 +640,11 @@ private function removegroup($group = null, $username = null, $email = null): vo
             $group = $this->prompt('Group', null, 'required');
         }
 
+        // Validate the group
+        if (! $this->validateGroup($group)) {
+            throw new CancelException('Invalid group: "' . $group . '"');
+        }
+
         $user = $this->findUser('Remove user from group', $username, $email);
 
         $confirm = $this->prompt(