TokenAuthentication: Allow custom keyword in the header

This allows subclassing TokenAuthentication and setting custom keyword,
thus allowing the Authorization header to be for example:

    Bearer 956e252a-513c-48c5-92dd-bfddc364e812

It doesn't change the behavior of TokenAuthentication itself,
it simply allows to reuse the logic of TokenAuthentication without
the need of copy pasting the class and changing one hardcoded string.

Related: #4080

rest_framework/authentication.py

@@ -150,6 +150,7 @@ class TokenAuthentication(BaseAuthentication):
         Authorization: Token 401f7ac837da42b97f613d789819ff93537bee6a
     """
 
+    keyword = 'Token'
     model = None
 
     def get_model(self):
@@ -168,7 +169,7 @@ def get_model(self):
     def authenticate(self, request):
         auth = get_authorization_header(request).split()
 
-        if not auth or auth[0].lower() != b'token':
+        if not auth or auth[0].lower() != self.keyword.lower().encode():
             return None
 
         if len(auth) == 1:
@@ -199,4 +200,4 @@ def authenticate_credentials(self, key):
         return (token.user, token)
 
     def authenticate_header(self, request):
-        return 'Token'
+        return self.keyword

tests/test_authentication.py

@@ -35,6 +35,10 @@ class CustomTokenAuthentication(TokenAuthentication):
     model = CustomToken
 
 
+class CustomKeywordTokenAuthentication(TokenAuthentication):
+    keyword = 'Bearer'
+
+
 class MockView(APIView):
     permission_classes = (permissions.IsAuthenticated,)
 
@@ -53,6 +57,7 @@ def put(self, request):
     url(r'^basic/$', MockView.as_view(authentication_classes=[BasicAuthentication])),
     url(r'^token/$', MockView.as_view(authentication_classes=[TokenAuthentication])),
     url(r'^customtoken/$', MockView.as_view(authentication_classes=[CustomTokenAuthentication])),
+    url(r'^customkeywordtoken/$', MockView.as_view(authentication_classes=[CustomKeywordTokenAuthentication])),
     url(r'^auth-token/$', 'rest_framework.authtoken.views.obtain_auth_token'),
     url(r'^auth/', include('rest_framework.urls', namespace='rest_framework')),
 ]
@@ -166,6 +171,7 @@ class BaseTokenAuthTests(object):
     urls = 'tests.test_authentication'
     model = None
     path = None
+    header_prefix = 'Token '
 
     def setUp(self):
         self.csrf_client = APIClient(enforce_csrf_checks=True)
@@ -179,31 +185,31 @@ def setUp(self):
 
     def test_post_form_passing_token_auth(self):
         """Ensure POSTing json over token auth with correct credentials passes and does not require CSRF"""
-        auth = 'Token ' + self.key
+        auth = self.header_prefix + self.key
         response = self.csrf_client.post(self.path, {'example': 'example'}, HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
     def test_fail_post_form_passing_nonexistent_token_auth(self):
         # use a nonexistent token key
-        auth = 'Token wxyz6789'
+        auth = self.header_prefix + 'wxyz6789'
         response = self.csrf_client.post(self.path, {'example': 'example'}, HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, status.HTTP_401_UNAUTHORIZED)
 
     def test_fail_post_form_passing_invalid_token_auth(self):
         # add an 'invalid' unicode character
-        auth = 'Token ' + self.key + "¸"
+        auth = self.header_prefix + self.key + "¸"
         response = self.csrf_client.post(self.path, {'example': 'example'}, HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, status.HTTP_401_UNAUTHORIZED)
 
     def test_post_json_passing_token_auth(self):
         """Ensure POSTing form over token auth with correct credentials passes and does not require CSRF"""
-        auth = "Token " + self.key
+        auth = self.header_prefix + self.key
         response = self.csrf_client.post(self.path, {'example': 'example'}, format='json', HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
     def test_post_json_makes_one_db_query(self):
         """Ensure that authenticating a user using a token performs only one DB query"""
-        auth = "Token " + self.key
+        auth = self.header_prefix + self.key
 
         def func_to_test():
             return self.csrf_client.post(self.path, {'example': 'example'}, format='json', HTTP_AUTHORIZATION=auth)
@@ -273,6 +279,12 @@ class CustomTokenAuthTests(BaseTokenAuthTests, TestCase):
     path = '/customtoken/'
 
 
+class CustomKeywordTokenAuthTests(BaseTokenAuthTests, TestCase):
+    model = Token
+    path = '/customkeywordtoken/'
+    header_prefix = 'Bearer '
+
+
 class IncorrectCredentialsTests(TestCase):
     def test_incorrect_credentials(self):
         """