feat: add new field sequenceIndex to message

src/things/message.ts

@@ -51,6 +51,11 @@ export interface SCMessageWithoutReferences
    */
   messageBody: string;
 
+  /**
+   * An index for applying a custom sorting of multiple messages
+   */
+  sequenceIndex?: number;
+
   /**
    * Translated fields of a message
    */
@@ -119,6 +124,7 @@ export class SCMessageMeta
       audiences: 'Zielgruppen',
       dateCreated: 'Erstellungsdatum',
       messageBody: 'Nachrichteninhalt',
+      sequenceIndex: 'Sequenzindex',
     },
     en: {
       ...SCCreativeWorkMeta.getInstance<SCCreativeWorkMeta>().fieldTranslations
@@ -127,6 +133,7 @@ export class SCMessageMeta
       audiences: 'audiences',
       dateCreated: 'date created',
       messageBody: 'message body',
+      sequenceIndex: 'sequence index',
     },
   };