Disallow updating event organizer

It does not make sense to update the organizer. It is up to EWS app to
handle the service user changes.

This fixes being unable to cancel the meeting from Eliona after updating
times in Outlook for bookings not made by Exchange users.

conf/conf.go

@@ -96,7 +96,7 @@ func UpsertEvent(ctx context.Context, assetIDs []int32, organizer string, startT
 
 	var dbEvent *appdb.Event
 	if eventID != 0 {
-		dbEvent, err = updateEvent(ctx, tx, eventID, organizer, startTime, endTime)
+		dbEvent, err = updateEvent(ctx, tx, eventID, startTime, endTime)
 	} else {
 		dbEvent, err = insertEvent(ctx, tx, organizer, startTime, endTime)
 	}
@@ -124,17 +124,15 @@ func insertEvent(ctx context.Context, tx *sql.Tx, organizer string, startTime, e
 	return dbEvent, nil
 }
 
-func updateEvent(ctx context.Context, tx *sql.Tx, eventID int64, organizer string, startTime, endTime time.Time) (*appdb.Event, error) {
+func updateEvent(ctx context.Context, tx *sql.Tx, eventID int64, startTime, endTime time.Time) (*appdb.Event, error) {
 	dbEvent, err := appdb.FindEvent(ctx, tx, eventID)
 	if err != nil {
 		return nil, fmt.Errorf("finding event: %v", err)
 	}
-	dbEvent.Organizer = organizer
 	dbEvent.StartTime = startTime
 	dbEvent.EndTime = endTime
 
 	if _, err := dbEvent.Update(ctx, tx, boil.Whitelist(
-		appdb.EventColumns.Organizer,
 		appdb.EventColumns.StartTime,
 		appdb.EventColumns.EndTime,
 	)); err != nil {