Prevent the creation on users and groups with numeric characters only

Update regular expression validator to prevent user and group creation.

Fixes: https://pagure.io/freeipa/issue/7572

Signed-off-by: Armando Neto <abiagion@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

ipalib/constants.py

@@ -288,7 +288,9 @@ RENEWAL_REUSE_CA_NAME = 'dogtag-ipa-ca-renew-agent-reuse'
 CA_DBUS_TIMEOUT = 120
 
 # regexp definitions
-PATTERN_GROUPUSER_NAME = '^[a-zA-Z0-9_.][a-zA-Z0-9_.-]*[a-zA-Z0-9_.$-]?$'
+PATTERN_GROUPUSER_NAME = (
+    '(?!^[0-9]+$)^[a-zA-Z0-9_.][a-zA-Z0-9_.-]*[a-zA-Z0-9_.$-]?$'
+)
 
 # Kerberos Anonymous principal name
 ANON_USER = 'WELLKNOWN/ANONYMOUS'