Refs #36042 -- Raised ValueError when providing composite expressions to aggregates.

docs/ref/models/expressions.txt

@@ -1105,6 +1105,14 @@ calling the appropriate methods on the wrapped expression.
         ``UNNEST``, etc.) to skip optimization and be properly evaluated when
         annotations spawn rows themselves. Defaults to ``False``.
 
+    .. attribute:: allows_composite_expressions
+
+        .. versionadded:: 5.2
+
+        Tells Django that this expression allows composite expressions, for
+        example, to support :ref:`composite primary keys
+        <cpk-and-database-functions>`. Defaults to ``False``.
+
     .. method:: resolve_expression(query=None, allow_joins=True, reuse=None, summarize=False, for_save=False)
 
         Provides the chance to do any preprocessing or validation of