@dmlloyd let me know if you think this is going into the right direction.

There is still a lot of things to take care and to try. Here are a few things that I did:

• Optional registration of class mappers in the SmallRyeBuilder for proper validation.
• When a root cannot be found, one is created on the fly (experimental, I need to think better about this. We may want to merge with the current one).
• Support JavaBeans getter style method names
• Validation is only done for properties that have a registered root. For instance if we register the root server, we only validate the server namespace.
• Moved standalone API's to main package and rename annotations for consistency.
• Support empty root prefix.
• Use SmallRyeConfigs Default Values API.
• Fixes around Optional / Map mapping.

There is still a lot of things to work on (which I'm happy to do):

• More tests
• Improve SmallRyeConfig entry point APIs to access the Mapping
• Additional CDI Integration (after Allow consumers of SmallRyeConfigFactory to participate in the Config building. #369)