Example-SO-VaporJsonResponse provides a working example for the StackOverflow question "Making Vapor API response JSON API Spec compliant".
Each class and/or struct in the compound object ApiResponse complies with the Content protocol. The Content protocol includes the Codable protocol for JSON decoding and encoding.
The POST was checked with the RESTed macOS application using the file "Dish.request".
curl -i -X POST "http://127.0.0.1:8080/api/dish" \
-H "Content-Type: application/json" \
-d '{"course": "salad", \
"description": "flavorful Southwestern ethos", \
"price": 1.82, "title": "Aztec Salad"}'