Refs #33308 -- Deprecated support for passing encoded JSON string literals to JSONField & co.

JSON should be provided as literal Python objects an not in their
encoded string literal forms.

docs/topics/db/queries.txt

@@ -971,7 +971,7 @@ Storing and querying for ``None``
 
 As with other fields, storing ``None`` as the field's value will store it as
 SQL ``NULL``. While not recommended, it is possible to store JSON scalar
-``null`` instead of SQL ``NULL`` by using :class:`Value('null')
+``null`` instead of SQL ``NULL`` by using :class:`Value(None, JSONField())
 <django.db.models.Value>`.
 
 Whichever of the values is stored, when retrieved from the database, the Python
@@ -987,11 +987,13 @@ query for SQL ``NULL``, use :lookup:`isnull`::
 
     >>> Dog.objects.create(name='Max', data=None)  # SQL NULL.
     <Dog: Max>
-    >>> Dog.objects.create(name='Archie', data=Value('null'))  # JSON null.
+    >>> Dog.objects.create(
+    ...     name='Archie', data=Value(None, JSONField())  # JSON null.
+    ... )
     <Dog: Archie>
     >>> Dog.objects.filter(data=None)
     <QuerySet [<Dog: Archie>]>
-    >>> Dog.objects.filter(data=Value('null'))
+    >>> Dog.objects.filter(data=Value(None, JSONField())
     <QuerySet [<Dog: Archie>]>
     >>> Dog.objects.filter(data__isnull=True)
     <QuerySet [<Dog: Max>]>
@@ -1007,6 +1009,15 @@ Unless you are sure you wish to work with SQL ``NULL`` values, consider setting
     Storing JSON scalar ``null`` does not violate :attr:`null=False
     <django.db.models.Field.null>`.
 
+.. versionchanged:: 4.2
+
+    Support for expressing JSON ``null`` using ``Value(None, JSONField())`` was
+    added.
+
+.. deprecated:: 4.2
+
+    Passing ``Value("null")`` to express JSON ``null`` is deprecated.
+
 .. fieldlookup:: jsonfield.key
 
 Key, index, and path transforms