Adding an annotation with a space in the key silently fails

Per this issue over on powertools for Java: https://github.com/aws-powertools/powertools-lambda-java/issues/1499
If a user adds a trace annotation with a space in it, the annotation is silently not added to the trace.

It [looks like annotation keys have to be alphanumeric](https://docs.aws.amazon.com/xray/latest/devguide/xray-api-segmentdocuments.html#api-segmentdocuments-annotations) without spaces for X-Ray. It would be great if the X-Ray SDK could through a runtime exception or something, so we get some indication that the thing we are doing isn't going to work, rather than silently accepting bad data.

What do you think?