Allow POST, PATCH, DELETE for actions in ReadOnlyModelViewSet (#797)

Currently if you try to use `POST` for action in `ReadOnlyModelViewSet` you will get problems:
- with DRF UI you will loose data input forms
- `drf_yasg` package will not generate OpenAPI specifications for such actions

This behavior was added to `django-rest-framework-json-api` in version 2.8.0 by mistake:

Commit: 7abd764
Subject: remove disallowed PUT method. (#643)

Author: kolomenkin

AUTHORS

@@ -19,6 +19,7 @@ Raphael Cohen <[email protected]>
 Roberto Barreda <[email protected]>
 Rohith PR <[email protected]>
 santiavenda <[email protected]>
+Sergey Kolomenkin <https://kolomenkin.com>
 Tim Selman <[email protected]>
 Yaniv Peer <[email protected]>
 Mohammed Ali Zubair <[email protected]>

CHANGELOG.md

@@ -18,6 +18,7 @@ any parts of the framework not mentioned in the documentation should generally b
 
 * Avoid `AttributeError` for PUT and PATCH methods when using `APIView`
 * Clear many-to-many relationships instead of deleting related objects during PATCH on `RelationshipView`
+* Allow POST, PATCH, DELETE for actions in `ReadOnlyModelViewSet`. It was problematic since 2.8.0.
 
 ### Changed
 

rest_framework_json_api/views.py

@@ -210,7 +210,7 @@ class ModelViewSet(AutoPrefetchMixin,
 class ReadOnlyModelViewSet(AutoPrefetchMixin,
                            RelatedMixin,
                            viewsets.ReadOnlyModelViewSet):
-    http_method_names = ['get', 'head', 'options']
+    http_method_names = ['get', 'post', 'patch', 'delete', 'head', 'options']
 
 
 class RelationshipView(generics.GenericAPIView):