This interface represents an element in the HTTP request execution chain. Each element can
either be a decorator around another element that implements a cross cutting aspect or
a self-contained executor capable of producing a response for the given request.
Important: please note it is required for decorators that implement post execution aspects
or response post-processing of any sort to release resources associated with the response
by calling Closeable.close() methods in case of an I/O, protocol or
runtime exception, or in case the response is not propagated to the caller.