JWT configuration in Django - django

Question

I'm developing a Django application for Windows with Pyhton 2.7.15. I need to implement an authentication mechanism where if a user has a specific JWT token, he can browse the application (in other words, I just need to verify the token and not generate it). The token is very easy and maybe will be something like this:
Header
{
"alg": "HS256",
"typ": "JWT"
}
Payload
{
"iss": "customIssuer"
}
Signature
HMACSHA256(
base64UrlEncode(header) + "." +
base64UrlEncode(payload),
secret
)
To implement the verification's service, I installed the Rest framework JWT tools and I modifyed my setting.py in this way:
...
REST_FRAMEWORK = {
'DEFAULT_PERMISSION_CLASSES': (
'rest_framework.permissions.IsAuthenticated',
),
'DEFAULT_AUTHENTICATION_CLASSES': (
'rest_framework_jwt.authentication.JSONWebTokenAuthentication',
'rest_framework.authentication.TokenAuthentication'
),
}
JWT_AUTH = {
'JWT_ISSUER': 'customIssuer'
}
...
then I modifyed the urls.py:
...
from rest_framework_jwt.views import verify_jwt_token
urlpatterns = [
...
url(r'^api-token-verify/', verify_jwt_token),
...
]
Finally, using Postman, I tryed to send a POST request with the above token but I get a 400 Bad Error error with this body:
{
"non_field_errors": [
"Invalid payload."
]
}
Investigating about the reason I realize that I must add the username claim in the payload but I don't want to. It's possible to configure the application to ignore that claim?