Stop auto-generating PayPal-Request-Id

- Allow manual setting of PayPal-Request-Id

lib/PayPal/Rest/ApiContext.php

@@ -85,13 +85,19 @@ class ApiContext
      */
     public function getRequestId()
     {
-        if ($this->requestId == null) {
-            $this->requestId = $this->generateRequestId();
-        }
-
         return $this->requestId;
     }
 
+    /**
+     * Sets the request ID
+     *
+     * @param string $requestId the PayPal-Request-Id value to use
+     */
+    public function setRequestId($requestId)
+    {
+        $this->requestId = $requestId;
+    }
+
     /**
      * Resets the requestId that can be used to set the PayPal-request-id
      * header used for idempotency. In cases where you need to make multiple create calls