Move http write functions to writers.go

internal/server/rpc/writers.go

@@ -0,0 +1,33 @@
+package rpc
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+func write(w http.ResponseWriter, status int, msg any) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+
+	switch m := msg.(type) {
+	case RPCError, *RPCError,
+		RPCResponse, *RPCResponse:
+		data, err := json.Marshal(m)
+		if err != nil {
+			return err
+		}
+		_, err = w.Write(data)
+		return err
+	default:
+		return fmt.Errorf("invalid RPC structure: %T", msg)
+	}
+}
+
+func WriteRouterError(w http.ResponseWriter, status int, errm *RPCError) error {
+	return write(w, status, errm)
+}
+
+func WriteResponse(w http.ResponseWriter, response *RPCResponse) error {
+	return write(w, http.StatusOK, response)
+}