I think we should name, interfaceIClientConfigBuilder to ClientConfigBuilder and ClientConfigBuilder implementation to PolywrapClientConfigBuilder.
I believe, We should also rename addPackage, addWrapper to setPackage, setWrapper, etc. because add generally means adding something without overwriting while set will mean setting it and also conveys that it may overwrite. I think the usage of addInterfaceImplementations seems correct because we always add it to the list.