DRF 3.10 deprecated decorators

[n2ygk]

The drfmaster builds are currently failing due to a deprecation described in encode/django-rest-framework#6687:

@detail_route/@list_route (replaced by @action)

Here's a snippet showing the error:

____________________ ERROR collecting example/urls_test.py _____________________
ImportError while importing test module '/home/travis/build/django-json-api/django-rest-framework-json-api/example/urls_test.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
example/urls_test.py:4: in <module>
    from .api.resources.identity import GenericIdentity, Identity
example/api/resources/identity.py:4: in <module>
    from rest_framework.decorators import detail_route, list_route
E   ImportError: cannot import name 'detail_route' from 'rest_framework.decorators' (/home/travis/build/django-json-api/django-rest-framework-json-api/.tox/py37-df20-django22-drfmaster/lib/python3.7/site-packages/rest_framework/decorators.py)

[n2ygk]

Looks like a pretty easy fix. Set detail=True for detail, False for list:

def action(methods=None, detail=None, url_path=None, url_name=None, **kwargs):
    """
    Mark a ViewSet method as a routable action.

    Set the `detail` boolean to determine if this action should apply to
    instance/detail requests or collection/list requests.
    """

[n2ygk]

Unfortunately the @action decorator is relatively new, so simply replacing it breaks with drf<=3.7

[n2ygk]

The workaround wasn't terrible though. PR coming.

[sliverc]

This got fixed with #664