When using a JDBC driver not known by Play-Slick, user can now specify the Slick driver explicitly.

For example, when using MariaDB driver, one may add:

db.default.slickdriver="scala.slick.driver.MySQLDriver"


Bonus: When adding this feature, I've fixed random TestableDBActionTest failures by forcing org.h2.Driver initialization.

Before this fix, the TestableDBActionSpec depended on a previous H2 driver initialization. The result of the TestableDBActionSpec depended on race condition with DBSpec.