Add a log to the current trace

This API will attach a log line to the trace context of the traceId field passed. 1. To start a brand new trace, call global/traces with null traceId and we will create the trace with the first span and return it in the response body traceId field. It will look something like this : 00-0427951c0c0a82d422f30fbc1b18d1e1-a39b316aa5d96365-01 2. Then when the client does calls and it wants to be part of that trace, populate traceparent header with the traceId that was returned in the body of step 1. 3. If the client wants to add something onto an existing trace then call global/traces populating traceId in the body with the traceId you want to enrich. For all traceId's whether in headers or body or anywhere, it will ALWAYS be in format e.g. 00-0427951c0c0a82d422f30fbc1b18d1e1-a39b316aa5d96365-01