Describe the bug
Currently, when a client retrieves SAML metadata via api/v3/providers/saml/1/metadata/?download , Authentik returns a response with Content Type set to application/xml as expected. However, if the same client send a request with the Accept header, such as:

curl -v "http://localhost:9000/api/v3/providers/saml/1/metadata/?download" -H "Accept: application/xml"

Authentik will return a 406 response instead. This is because, by default, DJango renderer only supports JSON:

REST_FRAMEWORK = {
    'DEFAULT_RENDERER_CLASSES': [
        'rest_framework.renderers.JSONRenderer',
        'rest_framework.renderers.BrowsableAPIRenderer',
    ]
}

https://pypi.org/project/djangorestframework-xml/ might be required in order to handle such case.

To Reproduce
Steps to reproduce the behavior:
curl -v "http://localhost:9000/api/v3/providers/saml/1/metadata/?download" -H "Accept: application/xml"
vs
curl -v "http://localhost:9000/api/v3/providers/saml/1/metadata/?download"

The former will fail with 406 whereas the latter will succeed.

Expected behavior
The endpoint to retrieve SAML metadata should return the content even if Accept header is set.

Screenshots
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Logs
Output of docker-compose logs or kubectl logs respectively

Version and Deployment (please complete the following information):

• authentik version: 2024.12.0

Additional context
Add any other context about the problem here.