Fix usage of OAuth2Client.verifyIdToken in example

[aknuds1]

examples/verifyIdToken.js uses the old signature for OAuth2Client.verifyIdToken, this PR upgrades it to the new API.

[JustinBeckwith]

Thank you for catching this :) Could you also add the audience in the new options?

const ticket = await oAuth2Client.verifyIdToken({
  idToken: oAuth2Client.credentials.id_token,
  audience: keys.web.client_id
});

[aknuds1]

@JustinBeckwith I added a part audience: 'audience' to the verifyIdToken options, as I don't know what would be a sensible value for audience. Does this look OK to you or should I use some other value?

[aknuds1]

@JustinBeckwith I'm also wondering if verifyIdToken should be documented somewhere? I only find it in examples and tests.

[JustinBeckwith]

The audience should be set to keys.web.client_id :) On the docs piece - the readme can always be better, but at least we have a proper reference doc now at google.github.io/google-auth-library-nodejs/

[aknuds1]

@JustinBeckwith Oh, alright, I've updated the PR. The verifyIdToken test (test.oauth2.ts) doesn't follow this pattern though, should it be changed to read const result = await client.verifyIdToken({idToken, audience: CLIENT_ID, maxExpiry}); to be consistent?

I mean, when I read the test, I don't get the impression that the audience should correspond to the client ID so it's confusing :)

[Boboss74]

omg this is why it doesn't work... T-T

So, this doc need some update too
https://developers.google.com/identity/sign-in/web/backend-auth#send-the-id-token-to-your-server