Nice article! However, there are a few things to be improved. I see the Headers associated type (as some other types, that could be not so obvious for the beginners), but in the article it isn't mentioned. And I also think about retry() and recieve(on: ) things as it's performed on the not main thread. But anyway, good work!

P.S. I also prefer structs instead of enums, but I use struct for each endpoint.