fix(httpapi): phase 1 compliance — ERR-01, SEC-04, CDN client, scheduler docs

Co-authored-by: Cursor <[email protected]>

internal/httpapi/problem.go

@@ -2,9 +2,15 @@ package httpapi
 
 import (
 	"encoding/json"
+	"log"
 	"net/http"
 )
 
+const (
+	internalErrorDetail = "an internal error occurred"
+	badGatewayDetail    = "upstream request failed"
+)
+
 // Problem is RFC 9457 application/problem+json.
 type Problem struct {
 	Type     string         `json:"type,omitempty"`
@@ -34,3 +40,19 @@ func writeJSON(w http.ResponseWriter, status int, v any) {
 func writeNoContent(w http.ResponseWriter) {
 	w.WriteHeader(http.StatusNoContent)
 }
+
+// writeInternalError logs err server-side and returns a generic 500 problem (ERR-01).
+func writeInternalError(w http.ResponseWriter, operation string, err error) {
+	if err != nil {
+		log.Printf("httpapi: %s: %v", operation, err)
+	}
+	writeProblem(w, http.StatusInternalServerError, "Internal Error", internalErrorDetail)
+}
+
+// writeBadGateway logs err server-side and returns a generic 502 problem (ERR-01).
+func writeBadGateway(w http.ResponseWriter, operation string, err error) {
+	if err != nil {
+		log.Printf("httpapi: %s: %v", operation, err)
+	}
+	writeProblem(w, http.StatusBadGateway, "Bad Gateway", badGatewayDetail)
+}