Hi colleagues!
Often, while developing a frontend app or any other communication vs REST API, it is worth having a Swagger UI - a test UI for the REST API that follows Open API 2.0 spec. Usually, it is quite a handful as it lets have quick manual tests vs REST API and its responses and the data inside.
Recently I've introduced the Swagger support to the InterSystems IRIS FHIR template for FHIR R4 API:
How to get it working.