enable email editable

function custom_op_basic_customer_field($session_response_data){
     $openpos_customer_basic_fields = $session_response_data['setting']['openpos_customer_fields'];
     foreach($openpos_customer_basic_fields as $key => $field)
     {
        if($field['code'] == 'email')
        {
           $openpos_customer_basic_fields[$key]['editable'] = 'true';
        }
     }
    $session_response_data['setting']['openpos_customer_fields'] = $openpos_customer_basic_fields;

    return $session_response_data;
}
add_filter('op_get_login_cashdrawer_data','custom_op_basic_customer_field',20,1);

update email data

 add_action('op_update_customer_after',function($customer_id,$session_data,$customer_request_data){
    $email = isset($customer_request_data['email']) && $customer_request_data['email'] ? $customer_request_data['email'] : '';
    $user_obj = get_user_by('email', $email);
    if(!$user_obj){
        wp_update_user( array( 'ID' => $customer_id, 'user_email' => $email ) );
    }else{
        if($user_obj->ID != $customer_id)
        {
            throw new Exception('Email has beem used by other customer');
        }
        
    }
 },10,3);