Moving to a new domain, is it possible to save cookies?

Question

Nginx

There is a site running in the foo.com.ru zone
There is another zone, foo.ru
Both zones are processed by the same nginx. Now the foo.ru zone redirects to the foo.com.ru zone.
You need to do the opposite, that is, move from the foo.com.ru domain to foo.ru, while keeping user cookies so that they do not reauthorize.
Any recipes?

Answer 1

The user visits foo.com.ru , we
generate a random token , we
write the token to the database and the current sessionID
, we send the user to foo.ru/mega_auth?token=xxxx , we get
the token from the sessionID database, hand it to the user.