public static ClientPreprocessors of(HttpPreprocessor preprocessor) {
        return builder().add(preprocessor).build();
    }
Creates a new instance from a single {@link HttpPreprocessor}.

@param preprocessor the {@link HttpPreprocessor} that transforms an
                    {@link HttpPreClient} to another
core/src/main/java/com/linecorp/armeria/client/ClientPreprocessors.java