message: refactor: return type of getFormFields
diff: @@ -3,6 +3,10 @@ import { HttpClient } from "../http";
  type AppID = string | number;
  type Lang = "ja" | "en" | "zh" | "user" | "default";
  +type Properties = {
  + [fieldCode: string]: any;
  +};
  +
  export class AppClient {
  private client: HttpClient;
  @@ -10,7 +14,11 @@ export class AppClient {
  this.client = client;
  }
  - public async getFormFields(app: AppID, lang?: Lang, preview?: boolean) {
  + public async getFormFields<T extends Properties>(
  + app: AppID,
  + lang?: Lang,
  + preview?: boolean
  + ): Promise<{ properties: T; revision: string }> {
  const path = `/k/v1${preview ? "/preview" : ""}/app/form/fields.json`;
  return this.client.get(path, { app, lang });
  }
  