@Deprecated
    protected final O execute(SessionProtocol protocol, HttpMethod method, RequestTarget reqTarget,
                              I req, RequestOptions requestOptions) {
        return execute(protocol, endpointGroup(), method, reqTarget, req, requestOptions);
    }
Executes the specified {@link Request} via the delegate.

@param protocol the {@link SessionProtocol} to use
@param method the method of the {@link Request}
@param reqTarget the {@link RequestTarget} of the {@link Request}
@param req the {@link Request}
@param requestOptions the {@link RequestOptions} of the {@link Request}

@deprecated prefer {@link ClientOptions#clientPreprocessors()} to execute requests
core/src/main/java/com/linecorp/armeria/client/UserClient.java