Redis MIGRATE should allow AUTH with username and password

MIGRATE only support a password.

The MIGRATE command should support the ACL based authentication.

Some examples:

> MIGRATE host port key db to AUTH default foobar

> MIGRATE host port "" db to AUTH default foobar KEYS a b c

> MIGRATE host port "" db to AUTH alice p1pp0 KEYS a b c

Note: when no username is entered it should continue to work as before.

Comment From: antirez

Thanks, this is planned, will check your PR in the next days. Thank you.

Comment From: antirez

Hello @tgrall, thanks for your help, unfortunately the PR is not in line with Redis guidelines and I'm reimplementing it: to assume the username should not collide with other common option is not robust enough. Thanks!

Comment From: antirez

Implemented in 058c72728, closing, thank you for your help.