static BodyPart of(ContentDisposition contentDisposition, MediaType contentType, CharSequence content) {
        requireNonNull(content, "content");
        return of(contentDisposition, contentType, HttpData.ofUtf8(content));
    }
Returns a new UTF-8-encoded {@link BodyPart} using the specified {@link ContentDisposition},
{@link MediaType} and {@link CharSequence}.
core/src/main/java/com/linecorp/armeria/common/multipart/BodyPart.java