Verify google email exists

[EarthenSky]

We want to do some fancy checking to make sure a that the user owns the google account we give access to the organization; this is a nice sanity check.

We'll want to send a verification email to the address. We have a rudimentary email sending module.

See https://stackoverflow.com/questions/69412522/what-is-the-best-way-to-verify-an-email-address-if-it-actually-exist for more discussion on this problem

This should be implemented as a function in the google_api module. If it needs some kind of separate thread to do the transaction to verify, it should be as decoupled as is reasonable.