dovecot - Nov 2021 - Dovecot Proxy with OAuth2 Setting Question

Hi

I'm setting up a Dovecot Proxy Server to access Gmail.
But It doesn?t work.

I tried to configure Dovecot without proxy authentication.

passdb {
  driver = static
  args = nopasssword=y proxy=y proxy_mech=xoauth2 ...
}

It works fine. So far so good.
But with proxy authentication It does not work.

Many clients don't support Oauth2, so Dovecot needs to authenticate for
them.

Please tell me how to set up Dovecot Proxy with OAuth2.

Reference
https://doc.dovecot.org/configuration_manual/authentication/oauth2/

Dovecot 2.3.8

HAL Pyoco