serialisation Delay

src/php/time/Delay.php

@@ -115,6 +115,13 @@ class Delay {
     $this->repr = $repr;
   }
 
+  function __serialize(): array {
+    return [$this->dest, $this->repr];
+  }
+  function __unserialize(array $data): void {
+    [$this->dest, $this->repr] = $data;
+  }
+
   /** @var DateTime */
   protected $dest;