When consuming a REST API that uses Basic Authentication, it's possible to statically specify the Username and Password (REST API properties and Service Center). However, I've encountered many REST APIs out in the wild that use Basic Authentication not for access to the REST API but for per-app or per-user credentials. As a workaround it's possible to support this with an OnBeforeRequest and adding the Authentication header yourself, but that is pretty cumbersome. It would be very handy if the Platform supports out-of-the-box capabilities for dynamically setting the REST APIs Basic Authentication Username and Password.
Some posibilities:
1) A property "use dynamic Basic Authentication" which if set on the REST API causes every method to have two extra parameters for Username and Password;
2) An action that's exposed throught the REST API (comparable with the way actions are exposed through an entity) that allows setting the Username and Password once for a specific REST API.