Make calendar owner the event organizer

The ICS organizer was taken from the external link's
organizer parameter. The CalDAV backend only schedules
invitations when the organizer matches the calendar
owner, so invites never went out under that value. The
event now names the authenticated user's email address;
the link organizer remains the fallback for users
without a profile email and stays visible on the
confirm page as meeting information.

lib/Controller/CalendarController.php

@@ -198,6 +198,12 @@ class CalendarController extends Controller
             throw new \RuntimeException('No authenticated Nextcloud user.');
         }
 
+        /*
+         * The calendar owner must be the ICS organizer so the
+         * CalDAV backend schedules the invitations in their name.
+         */
+        $data['organizerEmail'] = $user->getEMailAddress() ?? '';
+
         $calendars = $this->findWritableCalendars($user->getUID());
 
         /*
@@ -582,8 +588,16 @@ class CalendarController extends Controller
             $builder->setLocation($data['location']);
         }
 
-        if ($data['organizer'] !== '') {
-            $builder->setOrganizer($data['organizer']);
+        /*
+         * Invitations come from the calendar owner, the
+         * organizer of the external link is the fallback.
+         */
+        $organizer = $data['organizerEmail'] !== ''
+            ? $data['organizerEmail']
+            : $data['organizer'];
+
+        if ($organizer !== '') {
+            $builder->setOrganizer($organizer);
         }
 
         /*