docs(media): add an example for using a custom JSON encoder

docs/user/faq.rst

@@ -915,6 +915,10 @@ Furthermore, different Internet media types such as YAML,
 types than JSON, either as part of the respective (de)serialization format, or
 via custom type extensions.
 
+.. seealso:: See :class:`falcon.media.json.JSONHandler` for an exmaple on how to
+          use a custom json encoder.
+
+
 Does Falcon set Content-Length or do I need to do that explicitly?
 ------------------------------------------------------------------
 Falcon will try to do this for you, based on the value of

falcon/media/json.py

@@ -94,6 +94,37 @@ class JSONHandler(BaseHandler):
             ),
         )
 
+    You can also override the default JSONEncoder by using a custom Encoder and
+    updating the media handlers for ``application/json`` type to use that::
+
+        import json
+        from datetime import datetime
+        from functools import partial
+
+        import falcon
+        from falcon import media
+
+        class DatetimeEncoder(json.JSONEncoder):
+            \"\"\"Json Encoder that supports datetime objects.\"\"\"
+
+            def default(self, obj):
+                if isinstance(obj, datetime):
+                    return obj.isoformat()
+                return super().default(obj)
+
+        app = falcon.App()
+
+        json_handler = media.JSONHandler(
+            dumps=partial(json.dumps, cls=DatetimeEncoder),
+        )
+        extra_handlers = {
+            'application/json': json_handler,
+        }
+
+        app.req_options.media_handlers.update(extra_handlers)
+        app.resp_options.media_handlers.update(extra_handlers)
+
+
     Keyword Arguments:
         dumps (func): Function to use when serializing JSON responses.
         loads (func): Function to use when deserializing JSON requests.