Resolve other properties

[jdiazcano]

Resolve other variables with some kind of syntax so you can just create a property based on another like test=a, ${test}hello -> ahello

[rocketraman]

At least for environment variables, a workaround is to define the HOCON like this:

foo = abc
foo = ${?FOO}

This does the environment variable based override directly in the HOCON via typesafe config.