protected Builder setResponse(ServletResponse response) {
            if (response != null) {
                ((WebSubjectContext) getSubjectContext()).setServletResponse(response);
            }
            return this;
        }
Called by the {@code WebSubject.Builder} constructor, this method places the response object in the
context map for later retrieval.

@param response the outgoing ServletRequest paired with the ServletRequest that triggered the creation of
                the {@code WebSubject} instance.
@return 'this' for method chaining.
web/src/main/java/org/apache/shiro/web/subject/WebSubject.java