feature #57903 [Mailer] Implement Postal mailer (jonasclaes)

This PR was squashed before being merged into the 7.2 branch.

Discussion
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[Mailer] Implement Postal mailer

| Q             | A
| ------------- | ---
| Branch?       | 7.2
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| License       | MIT

This will implement the Postal mailer.

API docs: https://apiv1.postalserver.io/controllers/send/message.html

Docs: symfony/symfony-docs#20088

Commits
-------

db84ab3021 [Mailer] Implement Postal mailer

Exception/UnsupportedSchemeException.php

@@ -60,6 +60,10 @@ class UnsupportedSchemeException extends LogicException
             'class' => Bridge\Mailchimp\Transport\MandrillTransportFactory::class,
             'package' => 'symfony/mailchimp-mailer',
         ],
+        'postal' => [
+            'class' => Bridge\Postal\Transport\PostalTransportFactory::class,
+            'package' => 'symfony/postal-mailer',
+        ],
         'postmark' => [
             'class' => Bridge\Postmark\Transport\PostmarkTransportFactory::class,
             'package' => 'symfony/postmark-mailer',

Tests/Exception/UnsupportedSchemeExceptionTest.php

@@ -24,6 +24,7 @@
 use Symfony\Component\Mailer\Bridge\Mailjet\Transport\MailjetTransportFactory;
 use Symfony\Component\Mailer\Bridge\Mailomat\Transport\MailomatTransportFactory;
 use Symfony\Component\Mailer\Bridge\MailPace\Transport\MailPaceTransportFactory;
+use Symfony\Component\Mailer\Bridge\Postal\Transport\PostalTransportFactory;
 use Symfony\Component\Mailer\Bridge\Postmark\Transport\PostmarkTransportFactory;
 use Symfony\Component\Mailer\Bridge\Resend\Transport\ResendTransportFactory;
 use Symfony\Component\Mailer\Bridge\Scaleway\Transport\ScalewayTransportFactory;
@@ -50,6 +51,7 @@ public static function setUpBeforeClass(): void
             MailjetTransportFactory::class => false,
             MailomatTransportFactory::class => false,
             MandrillTransportFactory::class => false,
+            PostalTransportFactory::class => false,
             PostmarkTransportFactory::class => false,
             ResendTransportFactory::class => false,
             ScalewayTransportFactory::class => false,
@@ -83,6 +85,7 @@ public static function messageWhereSchemeIsPartOfSchemeToPackageMapProvider(): \
         yield ['mailomat', 'symfony/mailomat-mailer'];
         yield ['mailpace', 'symfony/mail-pace-mailer'];
         yield ['mandrill', 'symfony/mailchimp-mailer'];
+        yield ['postal', 'symfony/postal-mailer'];
         yield ['postmark', 'symfony/postmark-mailer'];
         yield ['resend', 'symfony/resend-mailer'];
         yield ['scaleway', 'symfony/scaleway-mailer'];

Transport.php

@@ -24,6 +24,7 @@
 use Symfony\Component\Mailer\Bridge\Mailjet\Transport\MailjetTransportFactory;
 use Symfony\Component\Mailer\Bridge\Mailomat\Transport\MailomatTransportFactory;
 use Symfony\Component\Mailer\Bridge\MailPace\Transport\MailPaceTransportFactory;
+use Symfony\Component\Mailer\Bridge\Postal\Transport\PostalTransportFactory;
 use Symfony\Component\Mailer\Bridge\Postmark\Transport\PostmarkTransportFactory;
 use Symfony\Component\Mailer\Bridge\Resend\Transport\ResendTransportFactory;
 use Symfony\Component\Mailer\Bridge\Scaleway\Transport\ScalewayTransportFactory;
@@ -59,6 +60,7 @@ final class Transport
         MailomatTransportFactory::class,
         MailPaceTransportFactory::class,
         MandrillTransportFactory::class,
+        PostalTransportFactory::class,
         PostmarkTransportFactory::class,
         ResendTransportFactory::class,
         ScalewayTransportFactory::class,