docs: def register(cls, name, entrypoint):
          """ Register a new entrypoint
  
          :param str name: Key used by messages
          :param kser.entry.Entrypoint entrypoint: class to load
          :raises ValidationError: Invalid entry
          """
          if not issubclass(entrypoint, Entrypoint):
              raise ValidationError(
                  "Invalid type for entry '{}', MUST implement "
                  "kser.entry.Entrypoint".format(name),
                  extra=dict(entrypoint=name)
              )
          cls.ENTRYPOINTS[name] = entrypoint
          logger.debug("{}.Registered: {}".format(cls.__name__, name))