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

(Cherry-picked from cce3e1b)

agenda-services/src/main/java/org/exoplatform/agenda/util/NotificationUtils.java

@@ -935,6 +935,7 @@ public static final void addIcsFile(NotificationInfo notification, MessageInfo m
       byte[] bytes = output.toByteArray();
       attachment.setInputStream(new ByteArrayInputStream(bytes));
       attachment.setMimeType("text/calendar;charset=utf-8;method=PUBLISH");
+      attachment.setName("event.ics");
       messageInfo.addAttachment(attachment);
     } catch (IOException e) {
       throw new IllegalStateException("Unable to convert event '" + eventSummary + "' to iCal format", e);