Add ProblemDetails support and deprecate HttpErr

http/httpErr.go

@@ -1,6 +1,7 @@
 package http
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 )
@@ -9,8 +10,63 @@ import (
 // The error will have the given return code `code`
 // and a json encoded body with the field "id" set to `errId`
 // and a field "message" set to the `message`
+//
+// Deprecated: Use ProblemDetails or ProblemDetailsStatusOnly instead
 func HttpErr(w http.ResponseWriter, errId int, message string, code int) {
 	w.WriteHeader(code)
 	w.Header().Add("Content-Type", "application/json")
 	fmt.Fprintf(w, "{\"id\": %d, \"message\": \"%s\"}", errId, message)
 }
+
+// Write an RFC 9457 compliant problem details response
+// If details is not nil, it will be included.
+// If extras is not nil, each key-value pair will be included at
+// the root layer.
+// Keys in extras that would overwrite the default elements will be ignored.
+// Those would be "type", "status", "title" and "detail"
+func ProblemDetails(
+	w http.ResponseWriter,
+	statusCode int,
+	errorType string,
+	errorTitle string,
+	details *string,
+	extras map[string]any,
+) {
+	w.WriteHeader(statusCode)
+	w.Header().Add("Content-Type", "application/problem+json")
+	data := map[string]any{
+		"type":   errorType,
+		"status": statusCode,
+		"title":  errorTitle,
+	}
+	if details != nil {
+		data["detail"] = *details
+	}
+	if extras != nil {
+		for k, v := range extras {
+			if _, ok := data[k]; ok {
+				// Don't overwrite default fields
+				continue
+			}
+			data[k] = v
+		}
+	}
+	enc := json.NewEncoder(w)
+	enc.Encode(data)
+}
+
+// Write a simple problem details response.
+// It only provides the status code, as defined in RFC 9457, section 4.2.1
+func ProblemDetailsStatusOnly(w http.ResponseWriter, statusCode int) {
+	w.WriteHeader(statusCode)
+	w.Header().Add("Content-Type", "application/problem+json")
+	data := map[string]any{
+		"type":      "about:blank",
+		"title":     http.StatusText(statusCode),
+		"status":    statusCode,
+		"reference": "RFC 9457",
+	}
+
+	enc := json.NewEncoder(w)
+	enc.Encode(data)
+}