restore mandatory field on domain-formfields; add translated require message and correct error-placement of the message

Signed-off-by: Michael Kaufmann <d00p@froxlor.org>

lib/formfields/admin/domains/formfield.domains_add.php

@@ -140,7 +140,8 @@ return [
 						'type' => 'checkbox',
 						'values' => $ipsandports,
 						'value' => explode(',', Settings::Get('system.defaultip')),
-						'is_array' => 1
+						'is_array' => 1,
+						'mandatory' => true
 					],
 					'selectserveralias' => [
 						'label' => lng('admin.selectserveralias'),

lib/formfields/admin/domains/formfield.domains_edit.php

@@ -154,7 +154,8 @@ return [
 						'type' => 'checkbox',
 						'values' => $ipsandports,
 						'value' => $usedips,
-						'is_array' => 1
+						'is_array' => 1,
+						'mandatory' => true
 					],
 					'selectserveralias' => [
 						'label' => lng('admin.selectserveralias'),