Add --timeout flag to docker login command

Description

If the Registry application takes a long time to authenticate a user, the docker cli will cancel the request and return something like this:

Error response from daemon: Get https://myregistry.com/v2/: Get https://myregistry.com/service/token?
account=myaccount&client_id=docker&offline_token=true&service=myservice: net/http: request canceled
(Client.Timeout exceeded while awaiting headers) (Client.Timeout exceeded while awaiting headers)

We know that this happens when the Registry application (Harbor) uses Active Directory to authenticate and the user or account is part of many Active Directory groups.

I would like to know if it is possible to add a new flag (--timeout) to the login command to set the desired timeout to wait before cancelling the login request. If this is wanted, I can also work on the change.

Thanks

Start with the docker login command and trace the reported request-cancellation path. Determine how a user-supplied --timeout should affect the login request and where relevant command tests live. Done means the flag is supported and a login can wait for the configured duration without the current premature cancellation.