override fun contentType(): MediaType {
        return "application/xml".toMediaType()
      }

      override fun writeTo(sink: BufferedSink) {
        sink.writeUtf8("<el")
        sink.flush()
        throw IOException("failed to stream the XML")
      }
    }

    class ValidRequestBody : RequestBody() {
      override fun contentType(): MediaType {

04C4          ; valid                                  # 1.1  CYRILLIC SMALL LETTER KA WITH HOOK
04C5          ; mapped                 ; 04C6          # 3.2  CYRILLIC CAPITAL LETTER EL WITH TAIL
04C6          ; valid                                  # 3.2  CYRILLIC SMALL LETTER EL WITH TAIL
04C7          ; mapped                 ; 04C8          # 1.1  CYRILLIC CAPITAL LETTER EN WITH HOOK

// xn--qxa6a ("eu", Greek) : EU
// https://eurid.eu
ευ

// xn--mgbah1a3hjkrd ("Mauritania", Arabic) : MR
موريتانيا

// xn--node ("ge", Georgian Mkhedruli) : GE
გე

// xn--qxam ("el", Greek) : GR
// Hellenic Ministry of Infrastructure, Transport, and Networks
ελ

// xn--j6w193g ("Hong Kong", Chinese) : HK
// https://www.hkirc.hk
// Submitted by registry <******@****.***>