Repository: encode/django-rest-framework

Issue:
wrong schema generation for UUIDField
## Checklist

- [x] I have verified that that issue exists against the `master` branch of Django REST framework.
- [x] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
- [x] This is not a usage question. (Those should be directed to the [discussion group](https://groups.google.com/forum/#!forum/django-rest-framework) instead.)
- [x] This cannot be dealt with as a third party library. (We prefer new functionality to be [in the form of third party libraries](http://www.django-rest-framework.org/topics/third-party-resources/#about-third-party-packages) where possible.)
- [x] I have reduced the issue to the simplest possible case.
- [ ] I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

## Steps to reproduce
create model including UUIDField
models.py:

	class Planning(models.Model):
	    uuid = models.UUIDField(default=uuid.uuid4, unique=True, editable=False, verbose_name="UUID")
	    middleware = models.ForeignKey(Middleware, to_field='name',
		    verbose_name='Middleware', on_delete=models.CASCADE)

serializers.py:

	class PlanningSerializer(serializers.ModelSerializer):


	    class Meta:
		model = Planning
		fields = '__all__'


## Expected behavior

meta for serializer should return

	    "actions": {
		"POST": {
		    "uuid": {
		        "type": "string",
		        "required": true,
		        "read_only": false,
		        "label": "UUID"
		    },
## Actual behavior

meta for serializer returns

	    "actions": {
		"POST": {
		    "uuid": {
		        "type": "field",
		        "required": false,
		        "read_only": true,
		        "label": "UUID"
		    },


Discussion:

Resolving patch:
diff --git a/rest_framework/metadata.py b/rest_framework/metadata.py
--- a/rest_framework/metadata.py
+++ b/rest_framework/metadata.py
@@ -40,6 +40,7 @@ class SimpleMetadata(BaseMetadata):
         serializers.BooleanField: 'boolean',
         serializers.NullBooleanField: 'boolean',
         serializers.CharField: 'string',
+        serializers.UUIDField: 'string',
         serializers.URLField: 'url',
         serializers.EmailField: 'email',
         serializers.RegexField: 'regex',


Test patch:
diff --git a/tests/test_metadata.py b/tests/test_metadata.py
--- a/tests/test_metadata.py
+++ b/tests/test_metadata.py
@@ -84,6 +84,7 @@ class ExampleSerializer(serializers.Serializer):
                 )
             )
             nested_field = NestedField()
+            uuid_field = serializers.UUIDField(label="UUID field")
 
         class ExampleView(views.APIView):
             """Example view."""
@@ -172,7 +173,13 @@ def get_serializer(self):
                                 'label': 'B'
                             }
                         }
-                    }
+                    },
+                    'uuid_field': {
+                        "type": "string",
+                        "required": True,
+                        "read_only": False,
+                        "label": "UUID field",
+                    },
                 }
             }
         }