feat: 优化企业微信服务的access_token获取方法。

- 添加获取access_token的方法到WechatWorkService中
- 重构fetchApprovalDetail和fetchFile方法，改用新的getAccessToken方法替代accessToken
- 在fetchFile方法中删除不必要的fs.createWriteStream调用

src/service/wechatwork.service.ts

@@ -18,7 +18,16 @@ export class WechatWorkService {
     this.wxCorpId = process.env.WX_CORP_ID
     this.wxCorpSecret = process.env.WX_CORP_SECRET
   }
-
+  /**
+   * 获取access_token
+   * @returns access_token
+   */
+  public async getAccessToken() {
+    if (!this.accessToken || this.tokenExpire < Date.now()) {
+      await this.refreshAccessToken()
+    }
+    return this.accessToken
+  }
   /**
    * 获取微信企业号的access_token
    * https://developer.work.weixin.qq.com/resource/devtool
@@ -49,11 +58,12 @@ export class WechatWorkService {
    */
   public async fetchApprovalDetail(spNo: string) {
     const url = `${WX_API_HOST}/cgi-bin/oa/getapprovaldetail`
+    const access_token = await this.getAccessToken()
     let config: AxiosRequestConfig = {
       method: 'post',
       url,
       params: {
-        access_token: this.accessToken,
+        access_token,
       },
       data: {
         sp_no: spNo,
@@ -71,12 +81,13 @@ export class WechatWorkService {
    */
   public async fetchFile(mediaId: string) {
     const url = `${WX_API_HOST}/cgi-bin/media/get`
+    const access_token = await this.getAccessToken()
     let config: AxiosRequestConfig = {
       method: 'get',
       url,
       responseType: 'stream',
       params: {
-        access_token: this.accessToken,
+        access_token,
         media_id: mediaId,
       },
     }