Implement SHA-2 Authentication

[AlekSi]

https://mysqlserverteam.com/the-mysql-8-0-4-release-candidate-is-available/
https://dev.mysql.com/doc/refman/8.0/en/caching-sha2-pluggable-authentication.html

[lefred]

Hi, if are you looking for help ? Our MySQL connectors engineer will be please to answer all your questions and provide you directions to include new authentication plugins to your driver for MySQL X Protocol (and more). Please join #connectors in MySQL Community Slack (https://lefred.be/mysql-community-on-slack/)