Add note about contexts tutorial being out of date

Author: mhauru

developers/compiler/minituring-contexts/index.qmd

@@ -14,6 +14,8 @@ Pkg.instantiate();
 
 In the [Mini Turing]({{< meta minituring >}}) tutorial we developed a miniature version of the Turing language, to illustrate its core design. A passing mention was made of contexts. In this tutorial we develop that aspect of our mini Turing language further to demonstrate how and why contexts are an important part of Turing's design.
 
+Note: The way Turing actually uses contexts changed somewhat in releases 0.39 and 0.40. The content of this page remains relevant, the principles of how contexts operate remain the same, and concepts like leaf and parent contexts still exist. However, we've moved away from using contexts for quite as many things as we used to. Most importantly, whether to accumulate the log joint, log prior, or log likelihood is no longer done using different contexts. Please keep this in mind as you read this page: The principles remain, but the details have changed. We will update this page once the refactoring of internals that is happening around releases like 0.39 and 0.40 is done.
+
 # Mini Turing expanded, now with more contexts
 
 If you haven't read [Mini Turing]({{< meta minituring >}}) yet, you should do that first. We start by repeating verbatim much of the code from there. Define the type for holding values for variables: