[symfony/mailer] add 5.4 recipe with test dsn

symfony/mailer/5.4/config/packages/mailer.yaml

@@ -0,0 +1,8 @@
+framework:
+    mailer:
+        dsn: '%env(MAILER_DSN)%'
+
+when@test:
+    framework:
+        mailer:
+            dsn: null://null

symfony/mailer/5.4/manifest.json

@@ -0,0 +1,18 @@
+{
+    "copy-from-recipe": {
+        "config/": "%CONFIG_DIR%/"
+    },
+    "env": {
+        "#1": "MAILER_DSN=smtp://localhost"
+    },
+    "docker-compose": {
+        "docker-compose.override.yml": {
+            "services": [
+                "mailer:",
+                "  image: schickling/mailcatcher",
+                "  ports: [1025, 1080]"
+            ]
+        }
+    },
+    "aliases": ["mailer", "mail"]
+}

symfony/mailer/5.4/post-install.txt

@@ -0,0 +1,14 @@
+  * You're ready to send emails.
+
+  * If you want to send emails via a supported email provider, install
+    the corresponding bridge.
+    For instance, <info>composer require mailgun-mailer</> for Mailgun.
+
+  * If you want to send emails asynchronously:
+
+    1. Install the messenger component by running <info>composer require messenger</>;
+    2. Add <info>'Symfony\Component\Mailer\Messenger\SendEmailMessage': amqp</> to the
+       <info>config/packages/messenger.yaml</> file under <info>framework.messenger.routing</>
+       and replace <info>amqp</> with your transport name of choice.
+
+  * <fg=blue>Read</> the documentation at <comment>https://symfony.com/doc/master/mailer.html</>