[9.x] Add raw content property for mailables (#44703)

* Add raw mailable content property

* Fix constructor signature

* Fixed style

* formatting

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Mail/Mailable.php

@@ -1655,6 +1655,10 @@ private function ensureContentIsHydrated()
             $this->markdown($content->markdown);
         }
 
+        if ($content->htmlString) {
+            $this->html($content->htmlString);
+        }
+
         foreach ($content->with as $key => $value) {
             $this->with($key, $value);
         }

src/Illuminate/Mail/Mailables/Content.php

@@ -38,6 +38,13 @@ class Content
      */
     public $markdown;
 
+    /**
+     * The pre-rendered HTML of the message.
+     *
+     * @var string|null
+     */
+    public $htmlString;
+
     /**
      * The message's view data.
      *
@@ -53,16 +60,18 @@ class Content
      * @param  string|null  $text
      * @param  string|null  $markdown
      * @param  array  $with
+     * @param  string|null  $htmlString
      *
      * @named-arguments-supported
      */
-    public function __construct(string $view = null, string $html = null, string $text = null, $markdown = null, array $with = [])
+    public function __construct(string $view = null, string $html = null, string $text = null, $markdown = null, array $with = [], string $htmlString = null)
     {
         $this->view = $view;
         $this->html = $html;
         $this->text = $text;
         $this->markdown = $markdown;
         $this->with = $with;
+        $this->htmlString = $htmlString;
     }
 
     /**
@@ -115,6 +124,19 @@ public function markdown(string $view)
         return $this;
     }
 
+    /**
+     * Set the pre-rendered HTML for the message.
+     *
+     * @param  string  $html
+     * @return $this
+     */
+    public function htmlString(string $html)
+    {
+        $this->htmlString = $html;
+
+        return $this;
+    }
+
     /**
      * Add a piece of view data to the message.
      *