…in case you’re reusing the same in-memory user whilst updating it in the DB.

Closes #5016, closes #5066, closes #4102

Closes #4749.

This is the matching commit to the fix for `datetime` in #4256

STRICT_JSON controls the renderer & parser behavior on whether or not
to accept non-standard float values (NaN, Infinity).

* Add failing TZ tests for DateTimeField

- tests "current" timezone activation
- tests output for non-UTC timezones

* Update DateTimeField TZ aware/naive test output

* Fix DateTimeField TZ handling

* Add Release Note for BC change

## Description

The `choices` field for the `ChoiceField` class should be able to be edited after `ChoiceField.__init__` is called.

```
field = ChoiceField(choices=[1,2])
field.choices = [1]  # Should no longer allow `2` as a choice
```

Currently, you must update `choices`, `grouped_choices`, and `choice_strings_to_values` to achieve this. This P/R keeps `grouped_choices` and `choice_strings_to_values` in sync whenever the `choices` are edited.

* Add tests for schema exclusions

* Move exclusion check to should_include_endpoint

* Update docs

* Switch to using `schema = None`

* Test PendingDeprecationWarnings

* Add note to release notes.

* s/deprecated/pending deprecation/

* Add PR link to release notes

* Correct typo in test class name

* Test 'exclude_from_schema' deprecation warning message (#1)

* Correct deprecation warning message

* Test case for #5240
* Remove unnecessary strip()  from get_description

Closes #5240

* Adjust test case

* Initial Refactor Step

* Add descriptor class
* call from generator
* proxy back to generator for implementation.

* Move `get_link` to descriptor

* Move `get_description` to descriptor

* Remove need for generator in get_description

* Move get_path_fields to descriptor

* Move `get_serializer_fields` to descriptor

* Move `get_pagination_fields` to descriptor

* Move `get_filter_fields` to descriptor

* Move `get_encoding` to descriptor.

* Pass just `url` from SchemaGenerator to descriptor

* Make `view` a property

Encapsulates check for a view instance.

* Adjust API Reference docs

* Add `ManualSchema` class

* Refactor to `ViewInspector` plus `AutoSchema`

The interface then is **just** `get_link()`

* Add `manual_fields` kwarg to AutoSchema

* Add schema decorator for FBVs

* Adjust comments

* Docs: Provide full params in example

Ref feedback https://github.com/encode/django-rest-framework/pull/5354/files/b52e372f8f936204753b17fe7c9bfb517b93a045#r137254795

* Add docstring for ViewInstpector.__get__ descriptor method.

Ref https://github.com/encode/django-rest-framework/pull/5354#discussion_r137265022

* Make `schemas` a package.

* Split generators, inspectors, views.

* Adjust imports

* Rename to EndpointEnumerator

* Adjust ManualSchema to take `fields`

… and `description`.

Allows `url` and `action` to remain dynamic

* Add package/module docstrings

* Fix authtoken managment command username param

Clarify in docs that REMOTE_ADDR is part of the WSGI environ, not an HTTP header.

Add value repr to the assertion output in FieldValues tests

* Update get_object() example in permissions.md 

I'm a bit confused about the example that's provided in the 'Object level permissions' section.  Other examples (e.g. Tutorial 3 - Class Based Views) provided a pk to get_object().  It doesn't seem like this example has any way of identifying a specific object.  

Just in case I'm correct, I've prepared this pull request. But if I'm wrong, would it be possible for you to explain the example I modified?  

Many Thanks...

* Adjust patch

* Make status_code documentation more readable.

* Update status-codes.md

Fixed the MultipleFieldLookupMixin example to properly check for object level permission

Fix ModelSerializer custom named fields with source on model

Fix test crudely

Remove comment

* Updated supported values for the NullBooleanField.
* Added check for unhashable types in NullBooleanField.

Sometimes, probably in the upgrade from Django 1.9 to 1.10, a post with
empty content is forbidden by javascript, with the message "Please fill
in this field". Filling the form with '{}' allows an application/json
request to be submitted.

The API call itself works perfectly well with a post with empty content:
the interface shouldn't make assumptions about it.

DjangoModelPermissions should perform auth check before accessing the view's queryset

Fix doc for ErrorDetail

Fix test name

Unexpected result when passing empty body to RequestFactory