Gravity Form - Display list of Users as a dropdown (User ID is the value)

Gravity Form - Display list of Users as a dropdown.php

add_filter( 'gform_pre_render_FORM_ID', 'dna_user_list_dropdown' );
add_filter( 'gform_pre_validation_FORM_ID', 'dna_user_list_dropdown' );
add_filter( 'gform_pre_submission_filter_FORM_ID', 'dna_user_list_dropdown' );
add_filter( 'gform_admin_pre_render_FORM_ID', 'dna_user_list_dropdown' );


function dna_user_list_dropdown( $form ) {
 
  foreach ( $form['fields'] as &$field ) {

    if ( $field->type != 'post_custom_field' || strpos( $field->cssClass, 'author-list' ) === false ) {
        continue;
    }

    $args = array(
      'fields'  => array( 'ID', 'display_name' ),
    ); 

    $users    = get_users($args);
    $choices  = array();

    foreach ( $users as $user ) {

      $choices[] = array(
        'text' => $user->display_name,
        'value' => $user->ID
      );

    }

    $field->placeholder = 'Select a User';
    $field->choices     = $choices;

  }

  return $form;

}