I am running a second web application in addition to Wordpress/WooCommerce. When users log into the second application, I'd like to authenticate them against the WP instance. I am using the REST API for data queries, but that only allows authentication with a consumer key. The API doesn't provide endpoints for user authentication.
Given a username and password, how can I authenticate against a Wordpress/WooCommerce instance? (In other words, from outside the instance.)