Csaba Kos

This adds a `CompositePropagation` class, which allows one to use multiple propagations. The purpose is to allow people to more easily transition between various propagations by being able to extract...

**Feature:** https://github.com/openzipkin/brave/pull/1090 added MongoDB tracing for the synchronous clients (`com.mongodb.MongoClient` and `com.mongodb.client.MongoClient`) but left the instrumentation unimplemented for the asynchronous (`com.mongodb.async.MongoClient`) and reactive (`com.mongodb.reactivestreams.client.MongoClient`) clients. Implement tracing for the asynchronous...