Subclass of ConcurrentModel that automatically removes
the BindingResult object when its corresponding
target attribute is replaced through regular Map operations.
This is the class exposed to handler methods by Spring WebFlux,
typically consumed through a declaration of the
Model interface as a parameter type.
There is typically no need to create it within user code.
If necessary a handler method can return a regular java.util.Map,
likely a java.util.ConcurrentMap, for a pre-determined model.