Adding media_type in JWTAuthentication (#426)

The drf render BrowsableAPIRenderer is requiring
a media_type object when generating a generic form
that includes a content type field, error will occur
if JWTAuthentication class does't have media_type.

Co-authored-by: Li Xin <[email protected]>

rest_framework_simplejwt/authentication.py

@@ -22,6 +22,7 @@ class JWTAuthentication(authentication.BaseAuthentication):
     token provided in a request header.
     """
     www_authenticate_realm = 'api'
+    media_type = 'application/json'
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)