bring in khatru and eventstore.

eventstore/negentropy.go

@@ -0,0 +1,13 @@
+package eventstore
+
+import "context"
+
+var negentropySessionKey = struct{}{}
+
+func IsNegentropySession(ctx context.Context) bool {
+	return ctx.Value(negentropySessionKey) != nil
+}
+
+func SetNegentropy(ctx context.Context) context.Context {
+	return context.WithValue(ctx, negentropySessionKey, struct{}{})
+}