Etcd currently supports validating peers based on their TLS certificate's
CN field. The current best practice for creation and validation of TLS
certs is to use the Subject Alternative Name (SAN) fields instead, so that
a certificate might be issued with a unique CN and its logical
identities in the SANs.
This commit extends the peer validation logic to use Go's
`(*"crypto/x509".Certificate).ValidateHostname` function for name
validation, which allows SANs to be used for peer access control.
In addition, it allows name validation to be enabled on clients as well.
This is used when running Etcd behind an authenticating proxy, or as
an internal component in a larger system (like a Kubernetes master).
This commit adds two flags to etcdctl:
1. `--password` flag to etcdctl as a global option. It can be used for
specifying password for authentication required for the command
execution.
2. `--new-user-password` flag to `etcdctl user add`. It can be used
for specifying password of newly created user by the command.
The main motivation of the flags is allowing user to have : in its
name.
Fix https://github.com/coreos/etcd/issues/9691
It is almost same to Documentation/v2/authentication.md because a
major part of its user interface is shared with the v2 auth. The newly
added doc includes some refinements for the v3 auth.
