Agroal - Allow to configure transaction isolation level

[gsmet]

[gsmet]

@machi1990 if you're looking for some issues, this one shouldn't be too hard and it's in another subsystem.

Note that there is a DefaultDataSourceConfigTest in which you should add a check for the new property.

Tell me if you're interested.

[machi1990]

Hey @gsmet, sure I am interested. I'll take a look at this. Your ping was probably lost in my inbox that's why I took a little longer to get back.