问来自https://www.googleapis.com/oauth2/v4/token.的意外响应不给"access_token"，只给"id_token“

EN

{
  "type": "service_account",
  "project_id": "...",
  "private_key_id": "...",
  "private_key": "-----BEGIN PRIVATE KEY-----\nMII...NF0=\n-----END PRIVATE KEY-----\n",
  "client_email": "...",
  "client_id": "...",
  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
  "token_uri": "https://oauth2.googleapis.com/token",
  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
  "client_x509_cert_url": "..."
}

const jwt = require("jsonwebtoken");

const credentials = require("./credentials.json");

const corsHeaders = {
  "Content-Type": "application/json",
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "GET, HEAD, POST, OPTIONS",
  "Access-Control-Allow-Headers": "Authorization",
  "Access-Control-Allow-Credentials" : true,
}

async function main() {
  const JWTToken = jwt.sign({
    "iss": credentials.client_email,
    "sub": credentials.client_email,
    "scope": "https://texttospeech.googleapis.com/$discovery/rest?version=v1",
    //"aud": credentials.token_uri,
    "aud": "https://www.googleapis.com/oauth2/v4/token",
    "exp": Math.floor(+new Date() / 1000) + 60 * 45,
    "iat": Math.floor(+new Date() / 1000),
  }, credentials.private_key, {
    "algorithm": "RS256",
    "header": {
      "kid": credentials.private_key_id,
      "typ": "JWT",
      "alg": "RS256",
    }
  });

  const JWTBody = new URLSearchParams();

  JWTBody.append("grant_type", "urn:ietf:params:oauth:grant-type:jwt-bearer");
  JWTBody.append("assertion", JWTToken);
  
  let JWTResponse;
  
  try {
    //JWTResponse = await fetch("https://oauth2.googleapis.com/token", {
    JWTResponse = await fetch("https://www.googleapis.com/oauth2/v4/token", {
      method: "POST",
      body: JWTBody,
    });
  } catch (e) {
    console.error(e);
    return new Response(`${e.name}: ${e.message}`, {
      status: 500,
      statusText: "Internal Server Error",
      headers: new Headers(corsHeaders),
    });
  }
  
  let JWTResponseBody;

  if (JWTResponse.ok) {
    JWTResponseBody = await JWTResponse.json();

    console.log("JWT", JWTResponseBody);
    console.log("JWT ACCESS_TOKEN", JWTResponseBody["access_token"]);
  } else {
    console.error("HTTP status code: ", JWTResponse.status, JWTResponse.statusText, JWTResponse);
  
    return new Response("HTTP status code: " + JWTResponse.status + JWTResponse.statusText, {
      status: 500,
      statusText: "Internal Server Error",
      headers: new Headers(corsHeaders),
    });
  }

  const TTSGoogleAPIsEndpoint = new URL("https://texttospeech.googleapis.com");
  const TTSRESTResources = {
    synthesize: new URL("/v1/text:synthesize", TTSGoogleAPIsEndpoint),
    list: new URL("/v1/voices", TTSGoogleAPIsEndpoint),
  };

  let response;

  try {
    response = await fetch(TTSRESTResources.synthesize, {
      method: "POST",
      headers: new Headers({
        "Authorization": `Bearer ${JWTResponseBody["access_token"]}`,
        "Content-Type": "application/json; charset=utf-8",
      }),
      body: JSON.stringify({
        "audioConfig": {
          "audioEncoding": "LINEAR16",
          "pitch": 0,
          "speakingRate": 1
        },
        "input": {
          "ssml": "<speak> <emphasis level=\"strong\">To be</emphasis> <break time=\"200ms\"/> or not to be? </speak>"
        },
        "voice": {
          "languageCode": "en-US",
          "name": "en-US-Standard-A"
        }
      }),
    });
  } catch (e) {
    console.error(e);
    return new Response(`${e.name}: ${e.message}`, {
      status: 500,
      statusText: "Internal Server Error",
      headers: new Headers(corsHeaders),
    });
  }

  if (response.ok) {
    const audio = await response.json();

    console.log(audio);
  } else {
    console.error("HTTP status code: ", response.status, response.statusText);
    console.log(response.headers.get("WWW-Authenticate"));

    return new Response("HTTP status code: " + response.status + response.statusText, {
      status: 500,
      statusText: "Internal Server Error",
      headers: new Headers(corsHeaders),
    });
  }
}

main();

(node:53185) ExperimentalWarning: The Fetch API is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
JWT {
  id_token: 'eyJh ... THE ID_TOKEN ... BSZw'
}
JWT ACCESS_TOKEN undefined
HTTP status code:  401 Unauthorized
Bearer realm="https://accounts.google.com/", error="invalid_token"