@UnstableApi
    static WebClient of(HttpPreprocessor httpPreprocessor) {
        return builder(httpPreprocessor).build();
    }
Returns a new {@link WebClient} that is configured using the specified {@link HttpPreprocessor}
using the default {@link ClientFactory} and the default {@link ClientOptions}.

@param httpPreprocessor the preprocessor
core/src/main/java/com/linecorp/armeria/client/WebClient.java