docs: note validators dict/JSON fix in 3.2.0 release notes

Signed-off-by: Fernando Macedo <fgmacedo@gmail.com>

Author: fgmacedo

docs/releases/3.2.0.md

@@ -172,3 +172,20 @@ The engine now skips self-cancellation when the invocation's task is the current
 running task, letting the originating handler complete normally.
 
 [#627](https://github.com/fgmacedo/python-statemachine/pull/627).
+
+### `validators` in a dict/JSON transition definition are no longer dropped
+
+`create_machine_class_from_definition` (the dict/JSON adapter behind
+{func}`statemachine.io.load`) threaded `cond`, `unless`, `on`, `before` and
+`after` from each transition definition into the `Transition`, but not
+`validators`. A `validators` entry was silently ignored, so it never ran at
+`send()`, leaving dict/JSON-defined machines without the explicit-rejection
+channel (raise to abort with a reason) that `validators` provides. The
+`TransitionDict` type also mistyped `validators` as `bool`.
+
+`validators` is now materialized onto the `Transition` like the other callback
+specs, and the type was corrected to the same callback-spec union as
+`cond`/`unless`.
+
+[#628](https://github.com/fgmacedo/python-statemachine/issues/628),
+[#629](https://github.com/fgmacedo/python-statemachine/pull/629).