@get:JvmName("headers") val headers: Headers,
      @get:JvmName("body") val body: BufferedSource,
    ) : Closeable by body

    internal companion object {
      /** These options follow the boundary. */
      val afterBoundaryOptions =
        Options.of(
          // 0.  "\r\n"  More parts.
          "\r\n".encodeUtf8(),
          // 1.  "--"    No more parts.
          "--".encodeUtf8(),