Generate unique request ID for tracing backend API calls

[jwreagor]

Noting for the future, it's come up a couple times that it might be helpful for us to generate unique request IDs for tracing back end REST calls. I believe the Java client does something similar but I could be wrong.

[kwilczynski]

The Java client (https://github.com/joyent/java-triton) seem to do both, consume remote Request-Id header (for example, to annotate an exception with it, etc.), and also seem to be generate an unique request ID added to current logging context for the request, so that all the log lines associated with it have it added, as per:

main/java/com/joyent/triton/http/RequestIdInterceptor.java#L14-L36

Update: Corrected link. GitHub's permalink didn't work.