WP_REST_Meta_Fields::update_meta_value( int $object_id, string $meta_key, string $name, mixed $value )

	protected function update_meta_value( $object_id, $meta_key, $name, $value ) {
		$meta_type = $this->get_meta_type();
		if ( ! current_user_can(  "edit_{$meta_type}_meta", $object_id, $meta_key ) ) {
			return new WP_Error(
				'rest_cannot_update',
				/* translators: %s: custom field key */
				sprintf( __( 'Sorry, you are not allowed to edit the %s custom field.' ), $name ),
				array( 'key' => $name, 'status' => rest_authorization_required_code() )
			);
		}

		$meta_key   = wp_slash( $meta_key );
		$meta_value = wp_slash( $value );

		// Do the exact same check for a duplicate value as in update_metadata() to avoid update_metadata() returning false.
		$old_value = get_metadata( $meta_type, $object_id, $meta_key );

		if ( 1 === count( $old_value ) ) {
			if ( $old_value[0] === $meta_value ) {
				return true;
			}
		}

		if ( ! update_metadata( $meta_type, $object_id, $meta_key, $meta_value ) ) {
			return new WP_Error(
				'rest_meta_database_error',
				__( 'Could not update meta value in database.' ),
				array( 'key' => $name, 'status' => WP_Http::INTERNAL_SERVER_ERROR )
			);
		}

		return true;
	}