@Test void specialCharsInJson_PROTO3() {
    assertThat(
      SpanBytesDecoder.PROTO3.decodeOne(SpanBytesEncoder.PROTO3.encode(UTF8_SPAN)))
      .isEqualTo(UTF8_SPAN);
  }
This isn't a test of what we "should" accept as a span, rather that characters that trip-up
json don't fail in codec.
zipkin/src/test/java/zipkin2/codec/SpanBytesDecoderTest.java