Interactive clients should print a warning (or error?) when passwords will be transmitted in cleartext

MariaDB Server has two client authentication plugins that can transmit passwords in cleartext:

• dialog
• mysql_clear_password

It is generally recommended to use TLS encryption when using either of these two client authentication plugins to ensure that passwords are not transmitted in cleartext.

Currently, interactive clients do not raise a warning or error when either of these plugins are used without TLS encryption.

Folks like jcd, markus makela, and esa.korhonen might have some input on how to implement this in a way that works with other MariaDB products.