OAuth example should not infer org affiliation from the email field.

This example parses the user's email, returned from Google's authorization server, in order to determine if the user should have access:

https://github.com/AnswerDotAI/fasthtml-example/blob/6a985a7d00ff33a54a07aa9ff9a8dba77bbeb428/oauth_example/oa.py#L9

However, Google says not to do this, and to use the "hd claim" instead:


We should update the example to follow Google's advice.

An analogous change will also be needed in the fasthtml explainer notebook: https://github.com/AnswerDotAI/fasthtml/blob/main/nbs/explains/oauth.ipynb

It may appear elsewhere as well.