missing documentation of AutoSchema

Author: n2ygk

docs/usage.md

@@ -32,6 +32,7 @@ REST_FRAMEWORK = {
         'rest_framework.renderers.BrowsableAPIRenderer'
     ),
     'DEFAULT_METADATA_CLASS': 'rest_framework_json_api.metadata.JSONAPIMetadata',
+    'DEFAULT_SCHEMA_CLASS': 'rest_framework_json_api.schemas.openapi.AutoSchema',
     'DEFAULT_FILTER_BACKENDS': (
         'rest_framework_json_api.filters.QueryParameterValidationFilter',
         'rest_framework_json_api.filters.OrderingFilter',
@@ -882,6 +883,8 @@ The `prefetch_related` case will issue 4 queries, but they will be small and fas
 DRF 3.10 added a new management command: `generateschema` which can generate an
 [OAS 3.0 schema](https://www.openapis.org/) as a YAML or JSON file.
 
+### Settings needed
+
 In order to produce an OAS schema that properly represents the JSON:API structure,
 DJA has this same command as an override of DRF's. In order to make sure the DJA
 version of the command is used, you must add DJA **ahead of** DRF in the
@@ -902,12 +905,58 @@ INSTALLED_APPS = [
 ]
 ```
 
+You'll also need to make sure you are using the DJA AutoSchema class, either as the default schema class:
+
+```python
+REST_FRAMEWORK = {
+    # ...
+    'DEFAULT_SCHEMA_CLASS': 'rest_framework_json_api.schemas.openapi.AutoSchema',
+}
+```
+
+### View-based
+
+Or you can explicit use DJA's AutoSchema it in your view definition, possible including an OAS schema document
+initializer:
+
+```python
+from rest_framework_json_api.schemas.openapi import AutoSchema
+
+openapi_schema = {
+    'info': {
+        'version': '1.0',
+        'title': 'my demo API',
+        'description': 'A demonstration of [OAS 3.0](https://www.openapis.org) AutoSchema',
+        'contact': {
+            'name': 'my name'
+        },
+        'license': {
+            'name': 'BSD 2 clause',
+            'url': 'https://github.com/django-json-api/django-rest-framework-json-api/blob/master/LICENSE',
+        }
+    },
+    'servers': [
+        {'url': 'https://localhost/v1', 'description': 'local docker'},
+        {'url': 'http://localhost:8000/v1', 'description': 'local dev'},
+        {'url': 'https://api.example.com/v1', 'description': 'demo server'},
+        {'url': '{serverURL}', 'description': 'provide your server URL',
+         'variables': {'serverURL': {'default': 'http://localhost:8000/v1'}}}
+    ]
+}
+
+
+class MyViewSet(ModelViewSet):
+    schema = AutoSchema(openapi_schema=openapi_schema)
+```
+
 To generate an OAS schema document, use something like:
 
 ```text
 $ django-admin generateschema --settings=example.settings >myschema.yaml
 ```
 
+
+
 You can then use any number of OAS tools such as
 [swagger-ui-watcher](https://www.npmjs.com/package/swagger-ui-watcher)
 to render the schema: