FIX #30010 : Use conf TICKET_MESSAGE_MAIL_INTRO instead of translation key (#30081)

* Use conf TICKET_MESSAGE_MAIL_INTRO instead of translation key

* Set TicketMessageMailIntroText as default value if conf empty

htdocs/ticket/class/ticket.class.php

@@ -2598,7 +2598,7 @@ class Ticket extends CommonObject
 							$subject = '['.$label_title.'- ticket #'.$object->track_id.'] '.$langs->trans('TicketNewMessage');
 
 							// Message send
-							$message = $langs->trans('TicketMessageMailIntroText');
+							$message = getDolGlobalString('TICKET_MESSAGE_MAIL_INTRO', $langs->trans('TicketMessageMailIntroText'));
 							$message .= '<br><br>';
 							$messagePost = GETPOST('message', 'restricthtml');
 							if (!dol_textishtml($messagePost)) {
@@ -2650,7 +2650,7 @@ class Ticket extends CommonObject
 							$message_intro = $langs->trans('TicketNotificationEmailBody', "#".$object->id);
 							$message_signature = GETPOST('mail_signature') ? GETPOST('mail_signature') : getDolGlobalString('TICKET_MESSAGE_MAIL_SIGNATURE');
 
-							$message = $langs->trans('TicketMessageMailIntroText');
+							$message = getDolGlobalString('TICKET_MESSAGE_MAIL_INTRO', $langs->trans('TicketMessageMailIntroText'));
 							$message .= '<br><br>';
 							$messagePost = GETPOST('message', 'restricthtml');
 							if (!dol_textishtml($messagePost)) {