Fixed #12990, Refs #27694 -- Added JSONField model field.

Thanks to Adam Johnson, Carlton Gibson, Mariusz Felisiak, and Raphael
Michel for mentoring this Google Summer of Code 2019 project and
everyone else who helped with the patch.

Special thanks to Mads Jensen, Nick Pope, and Simon Charette for
extensive reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

docs/ref/contrib/postgres/fields.txt

@@ -16,8 +16,7 @@ Indexes such as :class:`~django.contrib.postgres.indexes.GinIndex` and
 :class:`~django.contrib.postgres.indexes.GistIndex` are better suited, though
 the index choice is dependent on the queries that you're using. Generally, GiST
 may be a good choice for the :ref:`range fields <range-fields>` and
-:class:`HStoreField`, and GIN may be helpful for :class:`ArrayField` and
-:class:`JSONField`.
+:class:`HStoreField`, and GIN may be helpful for :class:`ArrayField`.
 
 ``ArrayField``
 ==============
@@ -517,96 +516,14 @@ using in conjunction with lookups on
     of the JSON which allows indexing. The trade-off is a small additional cost
     on writing to the ``jsonb`` field. ``JSONField`` uses ``jsonb``.
 
+.. deprecated:: 3.1
+
+    Use :class:`django.db.models.JSONField` instead.
+
 Querying ``JSONField``
 ----------------------
 
-We will use the following example model::
-
-    from django.contrib.postgres.fields import JSONField
-    from django.db import models
-
-    class Dog(models.Model):
-        name = models.CharField(max_length=200)
-        data = JSONField()
-
-        def __str__(self):
-            return self.name
-
-.. fieldlookup:: jsonfield.key
-
-Key, index, and path lookups
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-To query based on a given dictionary key, use that key as the lookup name::
-
-    >>> Dog.objects.create(name='Rufus', data={
-    ...     'breed': 'labrador',
-    ...     'owner': {
-    ...         'name': 'Bob',
-    ...         'other_pets': [{
-    ...             'name': 'Fishy',
-    ...         }],
-    ...     },
-    ... })
-    >>> Dog.objects.create(name='Meg', data={'breed': 'collie', 'owner': None})
-
-    >>> Dog.objects.filter(data__breed='collie')
-    <QuerySet [<Dog: Meg>]>
-
-Multiple keys can be chained together to form a path lookup::
-
-    >>> Dog.objects.filter(data__owner__name='Bob')
-    <QuerySet [<Dog: Rufus>]>
-
-If the key is an integer, it will be interpreted as an index lookup in an
-array::
-
-    >>> Dog.objects.filter(data__owner__other_pets__0__name='Fishy')
-    <QuerySet [<Dog: Rufus>]>
-
-If the key you wish to query by clashes with the name of another lookup, use
-the :lookup:`jsonfield.contains` lookup instead.
-
-If only one key or index is used, the SQL operator ``->`` is used. If multiple
-operators are used then the ``#>`` operator is used.
-
-To query for ``null`` in JSON data, use ``None`` as a value::
-
-    >>> Dog.objects.filter(data__owner=None)
-    <QuerySet [<Dog: Meg>]>
-
-To query for missing keys, use the ``isnull`` lookup::
-
-    >>> Dog.objects.create(name='Shep', data={'breed': 'collie'})
-    >>> Dog.objects.filter(data__owner__isnull=True)
-    <QuerySet [<Dog: Shep>]>
-
-.. warning::
-
-    Since any string could be a key in a JSON object, any lookup other than
-    those listed below will be interpreted as a key lookup. No errors are
-    raised. Be extra careful for typing mistakes, and always check your queries
-    work as you intend.
-
-Containment and key operations
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. fieldlookup:: jsonfield.contains
-.. fieldlookup:: jsonfield.contained_by
-.. fieldlookup:: jsonfield.has_key
-.. fieldlookup:: jsonfield.has_any_keys
-.. fieldlookup:: jsonfield.has_keys
-
-:class:`~django.contrib.postgres.fields.JSONField` shares lookups relating to
-containment and keys with :class:`~django.contrib.postgres.fields.HStoreField`.
-
-- :lookup:`contains <hstorefield.contains>` (accepts any JSON rather than
-  just a dictionary of strings)
-- :lookup:`contained_by <hstorefield.contained_by>` (accepts any JSON
-  rather than just a dictionary of strings)
-- :lookup:`has_key <hstorefield.has_key>`
-- :lookup:`has_any_keys <hstorefield.has_any_keys>`
-- :lookup:`has_keys <hstorefield.has_keys>`
+See :ref:`querying-jsonfield` for details.
 
 .. _range-fields:
 

docs/ref/contrib/postgres/forms.txt

@@ -164,8 +164,8 @@ Fields
 .. class:: JSONField
 
     A field which accepts JSON encoded data for a
-    :class:`~django.contrib.postgres.fields.JSONField`. It is represented by an
-    HTML ``<textarea>``.
+    :class:`~django.db.models.JSONField`. It is represented by an HTML
+    ``<textarea>``.
 
     .. admonition:: User friendly forms
 
@@ -173,6 +173,10 @@ Fields
         it is a useful way to format data from a client-side widget for
         submission to the server.
 
+    .. deprecated:: 3.1
+
+        Use :class:`django.forms.JSONField` instead.
+
 Range Fields
 ------------