add migration system

fix: protected variables (#30)

feat: basic message config abstraction

fix: use loader options in YamlFileConfigurator

feat: support comments in configs

feat: add support for more values in AbstractPlaceholderProvide

feat: add watchUpdateEvent in YamlDirectoryRepository

feat: add PersistentServerPlaceholder support

fix: enum serializer in YamlFileConfigurator

ref: create configs or config repositories