I have configured an external authentication in k8s by this annotation:
nginx.ingress.kubernetes.io/auth-url: "auth end point"
nginx.ingress.kubernetes.io/auth-method: GET
The external authenticator works with GET method.
The problem is with preflight requests (OPTIONS method). NGINX converts it in GET request and the authenticator return a 401 error (Authorization Required). Do you know how to fix it?