chore: convert the date object to json

Before this the output is:

"last_signature":"2025-08-23 00:36:23",
"current_date_time":"2025-08-23 00:36:24"

Now is:

"last_signature":"{\"date\":\"2025-08-23 01:35:36.000000\",\"timezone_type\":3,\"timezone\":\"UTC\"}",
"current_date_time":"{\"date\":\"2025-08-23 01:35:47.270345\",\"timezone_type\":3,\"timezone\":\"UTC\"}"

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Handler/SignEngine/SignEngineHandler.php

@@ -221,7 +221,10 @@ public function getLastSignedDate(): \DateTime {
 		// Prevent accepting certificates with future signing dates (possible clock issues)
 		$dateTime = new \DateTime();
 		if ($last['signingTime'] > $dateTime) {
-			$this->logger->error('We found Marty McFly', ['last_signature' => $last['signingTime'], 'current_date_time' => $dateTime]);
+			$this->logger->error('We found Marty McFly', [
+				'last_signature' => json_encode($last['signingTime']),
+				'current_date_time' => json_encode($dateTime),
+			]);
 			throw new \UnexpectedValueException('Invalid signingTime in certificate chain. We found Marty McFly');
 		}