Added created_by field value

app/Abstracts/Export.php

@@ -55,6 +55,11 @@ abstract class Export implements FromCollection, HasLocalePreference, ShouldAuto
         foreach ($this->fields as $field) {
             $value = $model->$field;
 
+            // created_by is equal to the owner id. Therefore, the value in export is owner email.
+            if ($field == 'created_by') {
+                $value = $model->owner->email ?? null;
+            }
+
             if (in_array($field, $date_fields)) {
                 $value = ExcelDate::PHPToExcel(Date::parse($value)->format('Y-m-d'));
             }