Async: add TargetedContinuation

This class enables us to consistently represent continuations
that are intended to be posted on a particular target handling
thread. It hols a sh_ptr to the caller so that the target thread
can re-enqueue the response on the caller after processing the
REQ/IND op.

include/asynchronousContinuation.h

@@ -3,6 +3,9 @@
 
 #include <functional>
 #include <memory>
+#include <componentThread.h>
+
+namespace smo {
 
 /**
  * AsynchronousContinuation - Template base class for async sequence management
@@ -47,4 +50,31 @@ protected:
 	OriginalCbFnT originalCbFn;
 };
 
+class ContinuationTarget
+{
+public:
+	ContinuationTarget(
+		const std::shared_ptr<ComponentThread> &caller)
+	: caller(caller)
+	{}
+
+public:
+	const std::shared_ptr<ComponentThread> caller;
+};
+
+template <class OriginalCbFnT>
+class TargetedAsynchronousContinuation
+:	public AsynchronousContinuation<OriginalCbFnT>, public ContinuationTarget
+{
+public:
+	TargetedAsynchronousContinuation(
+		const std::shared_ptr<ComponentThread> &caller,
+		OriginalCbFnT originalCbFn)
+	:	AsynchronousContinuation<OriginalCbFnT>(originalCbFn),
+		ContinuationTarget(caller)
+	{}
+};
+
+} // namespace smo
+
 #endif // ASYNCHRONOUS_CONTINUATION_H