better error handling when bad usage of system properties

[maxandersen]

in quarkusio/quarkus#30536 is found that if you put an object into system properties (object that is not a string) then smallrye config fails with a cryptic message.

java.util.ServiceConfigurationError: org.eclipse.microprofile.context.spi.ContextManagerExtension: io.smallrye.mutiny.context.MutinyContextManagerExtension not a subtype

Leaving users guessing what just failed.

o.smallrye.config.common.utils.ConfigSourceUtil.propertiesToMap(Properties) assumes all values can convert to meaningful string - that is not always the case.

I would expect:

a) if smallrye config insist on globally converting all properties in system properties and an error happens that the exception at least includes a hint of what key failed to convert
b) consider if it is reasonable to have all values in system properties be "toString"'able - should it maybe log an error or warning over failing hard?