feat: Dynamically build the my.cnf

[mkraeml]

The current Configure MySQL Client step is broken, as it overwrites instead of appends to the .my.cnf (> vs >>).
And as we already get all information for the MySQL connection from the DATABASE_URL, we can also extract those and fill the .my.cnf with it.

[shyim]

Why is overwriting a problem?

[mkraeml]

Why is overwriting a problem?

Overwriting is not directly a problem (my new code also overwrites the config), but we used > every time, so the file only has user=root as content instead of

[client]
host=127.0.0.1
user=root

And then the mysql client crashes because of a invalid config

[philipreinken]

I'd say LGTM - @shyim any blockers from your point of view?