Source

File: wp-includes/user.php

function wp_create_user_request( $email_address = '', $action_name = '', $request_data = array() ) {
	$email_address = sanitize_email( $email_address );
	$action_name   = sanitize_key( $action_name );

	if ( ! is_email( $email_address ) ) {
		return new WP_Error( 'invalid_email', __( 'Invalid email address.' ) );
	}

	if ( ! $action_name ) {
		return new WP_Error( 'invalid_action', __( 'Invalid action name.' ) );
	}

	$user    = get_user_by( 'email', $email_address );
	$user_id = $user && ! is_wp_error( $user ) ? $user->ID : 0;

	// Check for duplicates.
	$requests_query = new WP_Query(
		array(
			'post_type'     => 'user_request',
			'post_name__in' => array( $action_name ), // Action name stored in post_name column.
			'title'         => $email_address,        // Email address stored in post_title column.
			'post_status'   => array(
				'request-pending',
				'request-confirmed',
			),
			'fields'        => 'ids',
		)
	);

	if ( $requests_query->found_posts ) {
		return new WP_Error( 'duplicate_request', __( 'An incomplete request for this email address already exists.' ) );
	}

	$request_id = wp_insert_post(
		array(
			'post_author'   => $user_id,
			'post_name'     => $action_name,
			'post_title'    => $email_address,
			'post_content'  => wp_json_encode( $request_data ),
			'post_status'   => 'request-pending',
			'post_type'     => 'user_request',
			'post_date'     => current_time( 'mysql', false ),
			'post_date_gmt' => current_time( 'mysql', true ),
		),
		true
	);

	return $request_id;
}