Provide JDK type conversions

[Emily-Jiang]

As a user of the configuration API and/or injection mechanisms, I expect there to be a range of default value type conversions so that I can have configuration values of common JDK value types without having to explicitly enable or implement those conversions.
Source: #27 (comment)

[Emily-Jiang]

As app developer, I want to read single configured values of various other basic Java Types like int, Integer, long, LocalDate, LocalDateTime

Those are also used a lot in applications. It should be easy to consume configuration of those types out of the box.

This covers a Java class with valueOf, parse etc. These types should be an automatic converter class.

[tomas-langer]

As written, this would require reflection. I think we should not mandate reflection as part of this specification.
If we want to support valueOf or parse for ANY type, we would need to use reflection at runtime, which is against trends (and peformance).
If we still want to have support for additional types, we would need to add some way to mark such types, so they can be processed at build time.