Optimized MailManager::createSmtpTransport (#694)

* Update MailManager.php

* Revert "Update MailManager.php"

This reverts commit 1a9f6c9c6215a61d3136bd026879e9b5959e38fa.

* feat: Refactor MailManager.php to improve readability and maintainability

The code changes in `MailManager.php` refactor the `createSmtpTransport` method to improve readability and maintainability. The changes include type casting for certain configuration values and use of the null coalescing operator to handle missing values. This ensures that the method creates the SMTP transport correctly.

Note: This message has been generated based on the provided code changes and recent commits.

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Co-authored-by: Deeka Wong <8337659+huangdijia@users.noreply.github.com>

src/MailManager.php

@@ -203,7 +203,6 @@ protected function resolve(string $name): Mailer
     protected function createSmtpTransport(array $config): EsmtpTransport
     {
         $factory = new EsmtpTransportFactory();
-
         $scheme = $config['scheme'] ?? null;
 
         if (! $scheme) {
@@ -215,10 +214,10 @@ protected function createSmtpTransport(array $config): EsmtpTransport
         /** @var EsmtpTransport $transport */
         $transport = $factory->create(new Dsn(
             $scheme,
-            $config['host'],
-            $config['username'] ?? null,
-            $config['password'] ?? null,
-            $config['port'] ?? null,
+            (string) $config['host'],
+            isset($config['username']) ? ((string) $config['username']) : null,
+            isset($config['password']) ? ((string) $config['password']) : null,
+            isset($config['port']) ? ((int) $config['port']) : null,
             $config
         ));