code: public CRestBuilder extractsEntityAuthParamsWith(String entityContentType, EntityParamExtractor entityParamExtractor){
          this.httpEntityParamExtrators.put(entityContentType, entityParamExtractor);
          return this;
      }
docs: <p>Sets an entity parameters extractor for authenticated requests.</p>
  <p>When <b>CRest</b> is configured to authenticate requests, it uses an {@link org.codegist.crest.io.http.EntityParamExtractor} to extract parameters from the request entity to include them in the authentication process.</p>
  <p>A common use case is to deal with OAuth and multipart as some provider will use some multipart parameters and some not (binaries usually) in order to sign a request</p>
  @param entityContentType Entity Content-Type to bind the extractor to
  @param entityParamExtractor Extractor
  @return current builder