* @return array
	 */
	public static function activate_keys( $keys, $force = false ) {

		// Sanitize before sending.
		if ( ! is_array( $keys ) ) {
			$keys = explode( PHP_EOL, $keys );
		}

		$keys = array_map( 'sanitize_text_field', $keys );
		$keys = array_map( 'trim', $keys );
		$keys = array_unique( $keys );
		$keys = array_filter( $keys ); // Remove empty keys.

		$data = array(
			'keys' => $keys,
			'url'  => get_site_url(),
		);

		// Check for a cached result based on the keys and url input.
		$cache_hash = md5( wp_json_encode( $data ) );