Fixed #25995 -- Added an encoder option to JSONField

Thanks Berker Peksag and Tim Graham for the reviews.

docs/ref/contrib/postgres/fields.txt

@@ -458,17 +458,32 @@ using in conjunction with lookups on
 ``JSONField``
 =============
 
-.. class:: JSONField(**options)
+.. class:: JSONField(encoder=None, **options)
 
     A field for storing JSON encoded data. In Python the data is represented in
     its Python native format: dictionaries, lists, strings, numbers, booleans
     and ``None``.
 
-    If you want to store other data types, you'll need to serialize them first.
-    For example, you might cast a ``datetime`` to a string. You might also want
-    to convert the string back to a ``datetime`` when you retrieve the data
-    from the database. There are some third-party ``JSONField`` implementations
-    which do this sort of thing automatically.
+    .. attribute:: encoder
+
+        .. versionadded:: 1.11
+
+        An optional JSON-encoding class to serialize data types not supported
+        by the standard JSON serializer (``datetime``, ``uuid``, etc.). For
+        example, you can use the
+        :class:`~django.core.serializers.json.DjangoJSONEncoder` class or any
+        other :py:class:`json.JSONEncoder` subclass.
+
+        When the value is retrieved from the database, it will be in the format
+        chosen by the custom encoder (most often a string), so you'll need to
+        take extra steps to convert the value back to the initial data type
+        (:meth:`Model.from_db() <django.db.models.Model.from_db>` and
+        :meth:`Field.from_db_value() <django.db.models.Field.from_db_value>`
+        are two possible hooks for that purpose). Your deserialization may need
+        to account for the fact that you can't be certain of the input type.
+        For example, you run the risk of returning a ``datetime`` that was
+        actually a string that just happened to be in the same format chosen
+        for ``datetime``\s.
 
     If you give the field a :attr:`~django.db.models.Field.default`, ensure
     it's a callable such as ``dict`` (for an empty default) or a callable that

docs/releases/1.11.txt

@@ -129,6 +129,10 @@ Minor features
 * The new :class:`~django.contrib.postgres.indexes.GinIndex` class allows
   creating gin indexes in the database.
 
+* :class:`~django.contrib.postgres.fields.JSONField` accepts a new ``encoder``
+  parameter to specify a custom class to encode data types not supported by the
+  standard encoder.
+
 :mod:`django.contrib.redirects`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~