public interface BaggageContext
A BaggageContext is an opaque context object belonging to an execution. Baggage contexts are propagated
alongside requests as they execute -- they should be passed to new threads, included with work items (e.g.,
Runnable, Callable, etc.), serialized in network headers, and so on.
BaggageContext objects have no direct methods for manipulating contexts or accessing data that they carry.
This is because, in the common case, a BaggageContext is typically empty, and an empty context is typically
implemented using null values.
To propagate BaggageContext objects, call BaggageProvider methods such as
BaggageProvider.branch(BaggageContext), BaggageProvider.serialize(BaggageContext), etc.