[9.x] ability to add tags/metadata to Emails/Notifications

src/Illuminate/Mail/Mailable.php

@@ -20,6 +20,9 @@
 use PHPUnit\Framework\Assert as PHPUnit;
 use ReflectionClass;
 use ReflectionProperty;
+use Symfony\Component\Mailer\Header\MetadataHeader;
+use Symfony\Component\Mailer\Header\TagHeader;
+use Symfony\Component\Mime\Email;
 
 class Mailable implements MailableContract, Renderable
 {
@@ -870,6 +873,33 @@ public function attachData($data, $name, array $options = [])
         return $this;
     }
 
+    /**
+     * Add a tag header to the message when supported by the underlying transport.
+     *
+     * @param  string  $value
+     * @return $this
+     */
+    public function tag($value)
+    {
+        return $this->withSymfonyMessage(function (Email $message) use ($value) {
+            $message->getHeaders()->add(new TagHeader($value));
+        });
+    }
+
+    /**
+     * Add a metadata header to the message when supported by the underlying transport.
+     *
+     * @param  string  $key
+     * @param  string  $value
+     * @return $this
+     */
+    public function metadata($key, $value)
+    {
+        return $this->withSymfonyMessage(function (Email $message) use ($key, $value) {
+            $message->getHeaders()->add(new MetadataHeader($key, $value));
+        });
+    }
+
     /**
      * Assert that the given text is present in the HTML email body.
      *

src/Illuminate/Notifications/Messages/MailMessage.php

@@ -7,6 +7,9 @@
 use Illuminate\Contracts\Support\Renderable;
 use Illuminate\Mail\Markdown;
 use Illuminate\Support\Traits\Conditionable;
+use Symfony\Component\Mailer\Header\MetadataHeader;
+use Symfony\Component\Mailer\Header\TagHeader;
+use Symfony\Component\Mime\Email;
 
 class MailMessage extends SimpleMessage implements Renderable
 {
@@ -253,6 +256,33 @@ public function attachData($data, $name, array $options = [])
         return $this;
     }
 
+    /**
+     * Add a tag header to the message when supported by the underlying transport.
+     *
+     * @param  string  $value
+     * @return $this
+     */
+    public function tag($value)
+    {
+        return $this->withSymfonyMessage(function (Email $message) use ($value) {
+            $message->getHeaders()->add(new TagHeader($value));
+        });
+    }
+
+    /**
+     * Add a metadata header to the message when supported by the underlying transport.
+     *
+     * @param  string  $key
+     * @param  string  $value
+     * @return $this
+     */
+    public function metadata($key, $value)
+    {
+        return $this->withSymfonyMessage(function (Email $message) use ($key, $value) {
+            $message->getHeaders()->add(new MetadataHeader($key, $value));
+        });
+    }
+
     /**
      * Set the priority of this message.
      *