Document MySQL setup

[bemoty]

We need a template for our MySQL DB setup (tables, configuration, etc.)

--> we use the OLD auth mode for our sokka db user! nodejs 'mysql' dependency does not support MySQL 8 / devX SHA2 auth method.

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'pw';

also, please create an extra user for sokka with only one db! (no root user!)