XMLFile: fix assertion

Author: kockodev

src/Account/FioAccount.php

@@ -2,7 +2,9 @@
 
 namespace h4kuna\Fio\Account;
 
-class FioAccount
+use Stringable;
+
+class FioAccount implements Stringable
 {
 	private Bank $account;
 
@@ -31,7 +33,7 @@ public function getToken(): string
 	}
 
 
-	public function __toString()
+	public function __toString(): string
 	{
 		return $this->getAccount();
 	}

src/Pay/XMLFile.php

@@ -3,6 +3,7 @@
 namespace h4kuna\Fio\Pay;
 
 use h4kuna\Fio\Exceptions\InvalidState;
+use Stringable;
 use XMLWriter;
 
 class XMLFile
@@ -63,9 +64,9 @@ private function setBody(Payment\Property $data): self
 				$value = '';
 			}
 
-			assert(is_scalar($value));
+			assert(is_scalar($value) || $value instanceof Stringable);
 			$this->xml->startElement($node);
-			$this->xml->text(strval($value));
+			$this->xml->text((string) $value);
 			$this->xml->endElement();
 		}
 		$this->xml->endElement();