Add filter, add READMES

backend_go/http_helpers.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+)
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	enc := json.NewEncoder(w)
+	_ = enc.Encode(v)
+}
+
+func writeError(w http.ResponseWriter, status int, msg string) {
+	writeJSON(w, status, ErrorResponse{Detail: msg})
+}
+
+func decodeJSON(r io.Reader, dst any) error {
+	dec := json.NewDecoder(r)
+	return dec.Decode(dst)
+}