fix: Fix event attachement issue for some email inbox providers (#723)

Before this fix, the attachement was sent as raw text/Calendar without attachment name. This PR will add attachement name to avoid attachement lack in some mail inboxes

agenda-services/src/main/java/org/exoplatform/agenda/notification/builder/AgendaTemplateBuilder.java

@@ -164,6 +164,7 @@ protected MessageInfo makeMessage(NotificationContext ctx) {
                                        timeZone);
       attachment.setInputStream(new ByteArrayInputStream(icsFileBytes));
       attachment.setMimeType("text/calendar;charset=utf-8;method=PUBLISH");
+      attachment.setName("event.ics");
       messageInfo.addAttachment(attachment);