Authenticate officially via Google

[twcrews]

As it stands, the plugin is using a circumvention method to access a user's Google account. This is a flaky and usually temporary solution at best.

I imagine this has been tried, but I couldn't find any issues related to it: have we tried to use Google's native third-party app auth process? Or at least something like app-specific passwords?

Unless there's something specific to the Nest platform that blocks this, I'd be happy to give it a shot myself and send up a PR.

[louismcohen]

Home Assistant uses the proper Nest login configuration using real OAuth app credentials. It's somewhat cumbersome to set up (I did it the other week), but it is 100% legit:

https://www.home-assistant.io/integrations/nest/#configuration

[edlucky1]

Additional temperature sensors appear to not be supported using this method. Not sure if there are other devices or functionality not supported beyond that.

[twcrews]

Dropping this because, as mentioned, it would break support for temperature sensors.