It is possible to make REST API calls from within the product to various available endpoints. The page that is being used has the following URL:
niku/rest/describe/index.html
It is however noticed that whenever this page is used, an HTTP 401 is received. Using the same calls from a tool such as Postman works.
Version: 16.1.1
Unauthenticated session in Swagger.
Click on the Red exclamation mark (highlighted in the screenshot below). A pop-up opens up where username and password can be entered. Enter the relevant values. Click on "Authorize".