@Override
    public AbstractHttpMessageBuilder content(MediaType contentType, String content) {
        requireNonNull(contentType, "contentType");
        requireNonNull(content, "content");
        return content(contentType, HttpData.of(contentType.charset(StandardCharsets.UTF_8),
                                                content));
    }
Returns the {@link Publisher} that was set by {@link #content(MediaType, Publisher)}.
core/src/main/java/com/linecorp/armeria/common/AbstractHttpMessageBuilder.java