v2.0.0-RC2 - Future Directives Instrumentation

Fixes

• Triggers operation name resolution (and, as a side effect, taking a sampling decision) when a request hits any of the FutureDirectives. We are doing this because one of the most common uses of FutureDirectives is to grab call external system for authentication or getting data that is actually useful for request processing, which would probably be traced as well and we need to have both a sampling decision and operation name at this point.
• Include instrumentation for FastFuture, which is used in several places on the default directives. This instrumentation ensures that the Context of the original Futures will be kept when turning it into a FastFuture.
• Change the default client operation name to use the HTTP method instead of host.