refactor: message object properties

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

shared/lib/Mail/Object/MessagePartInterface.php

@@ -20,6 +20,19 @@ use KTXF\Json\JsonSerializable;
  */
 interface MessagePartInterface extends JsonSerializable {
 
+    public const PROPERTY_PART_ID = 'partId';
+    public const PROPERTY_BLOB_ID = 'blobId';
+    public const PROPERTY_BLOB_IDSIZE = 'size';
+    public const PROPERTY_NAME = 'name';
+    public const PROPERTY_TYPE = 'type';
+    public const PROPERTY_CHARSET = 'charset';
+    public const PROPERTY_DISPOSITION = 'disposition';
+    public const PROPERTY_CONTENT_ID = 'cid';
+    public const PROPERTY_LANGUAGE = 'language';
+    public const PROPERTY_LOCATION = 'location';
+    public const PROPERTY_CONTENT = 'content';
+    public const PROPERTY_SUB_PARTS = 'subParts';
+
     /**
      * Gets the blob identifier
      *
@@ -38,6 +51,15 @@ interface MessagePartInterface extends JsonSerializable {
      */
     public function getId(): ?string;
 
+    /**
+     * Gets the part size in bytes
+     *
+     * @since 2026.06.15
+     *
+     * @return int|null
+     */
+    public function getSize(): ?int;
+
     /**
      * Gets the MIME type
      *
@@ -56,6 +78,15 @@ interface MessagePartInterface extends JsonSerializable {
      */
     public function getDisposition(): ?string;
 
+    /**
+     * Gets the Content-ID for inline parts
+     *
+     * @since 2026.06.15
+     *
+     * @return string|null
+     */
+    public function getContentId(): ?string;
+
     /**
      * Gets the part name
      *
@@ -92,6 +123,15 @@ interface MessagePartInterface extends JsonSerializable {
      */
     public function getLocation(): ?string;
 
+    /**
+     * Gets the decoded part content
+     *
+     * @since 2026.06.15
+     *
+     * @return string|null
+     */
+    public function getContent(): ?string;
+
     /**
      * Gets the sub-parts
      *