Generate java from metadata

[alechenninger]

This is a little harder, but not much, thanks to: https://github.com/square/javapoet

[alechenninger]

From README...

This is lowest priority since java to metadata is lossy therefore going the other direction will require a small amount of "magic" to compute that missing information. For this reason I think it's better to simply use Java classes as the starting point / source of truth since they're much easier to write, usable in other code, and retain more information.

[alechenninger]

Another reason I found not to go this direction is correctness: it is much more difficult to have bugs in your metadata when your source of truth is strongly typed and statically analyzable.