text: -- supplier_custom_fields --
  SET SESSION sql_mode="NO_AUTO_CREATE_USER";
  
  ALTER TABLE `phppos_suppliers` 
  ADD `custom_field_1_value` VARCHAR(255) NULL DEFAULT NULL, 
  ADD INDEX (`custom_field_1_value`),
  
  ADD `custom_field_2_value` VARCHAR(255) NULL DEFAULT NULL, 
  ADD INDEX (`custom_field_2_value`),
  
  ADD `custom_field_3_value` VARCHAR(255) NULL DEFAULT NULL, 
  ADD INDEX (`custom_field_3_value`),
  
  ADD `custom_field_4_value` VARCHAR(255) NULL DEFAULT NULL, 
  ADD INDEX (`custom_field_4_value`),
  
  ADD `custom_field_5_value` VARCHAR(255) NULL DEFAULT NULL, 
  ADD INDEX (`custom_field_5_value`);