Autoriser tous les utilisateurs LDAP

Dans un premier temps.

* tmpl/sunstone-ldap_auth.conf: Activer :mapping_default.

Cherry-picked for 2.6.0 from 71e3fedc6a

Ref: #17841

tmpl/sunstone-ldap_auth.conf

@@ -30,6 +30,9 @@ server 1:
     # for Active Directory use this user_field instead
     #:user_field: 'sAMAccountName'
 
+    # Default group ID used for users in an AD group not mapped
+    :mapping_default: 1
+
 # List the order the servers are queried
 :order:
     - server 1