MySQL users can be configured to require a specific authentication
method when connecting to the MySQL server, e.g. GSSAPI, SHA-256
or ed25519.
Expose a new attribute $plugin, that is passed to puppetlabs-mysql
When creating/updating a user in the MySQL database.
Change-Id: I1c7b40d110190eba861ed466d2644c2f1abbf7b0
Related-Bug: #1866093