Support naming docker images on eggs; closes #4052

Bumps PTDL_v1 export images to PTDL_v2, updates the Minecraft specific eggs to use named images.

app/Models/Egg.php

@@ -12,7 +12,7 @@ namespace Pterodactyl\Models;
  * @property array|null $features
  * @property string $docker_image -- deprecated, use $docker_images
  * @property string $update_url
- * @property array $docker_images
+ * @property array<string, string> $docker_images
  * @property array|null $file_denylist
  * @property string|null $config_files
  * @property string|null $config_startup
@@ -50,6 +50,11 @@ class Egg extends Model
      */
     public const RESOURCE_NAME = 'egg';
 
+    /**
+     * Defines the current egg export version.
+     */
+    public const EXPORT_VERSION = 'PTDL_v2';
+
     /**
      * Different features that can be enabled on any given egg. These are used internally
      * to determine which types of frontend functionality should be shown to the user. Eggs