fix(core): update

ts/letter/classes.letterservice.ts

@@ -0,0 +1,17 @@
+import type { SzPlatformService } from '../classes.platformservice.js';
+import * as plugins from '../plugins.js';
+
+export interface ILetterConstructorOptions {
+  letterxpressUser: string;
+  letterxpressToken: string;
+}
+
+export class LetterService {
+  public platformServiceRef: SzPlatformService;
+  public options: ILetterConstructorOptions;
+
+  constructor(platformServiceRefArg: SzPlatformService, optionsArg: ILetterConstructorOptions) {
+    this.platformServiceRef = platformServiceRefArg;
+    this.options = optionsArg;
+  }
+}