NGIX to Apache for Digest Authentication

I have a NGINX in front of Apache which has both Basic and Digest
authentication turned on. I’d like a set up where a user connects to
NGINX (using Basic or Digest) and NGINX simply proxy the request to the
Apache where the actual authentication happens. I have the Basic case
working but not the Digest. Here’s how the config for Basic looks like:

location /basic {

      proxy_set_header x-user $http_x_user;
      proxy_pass       http://my.apache.server; // where 

authentication happens
proxy_set_header X-Original-URI $request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;

}
Could somebody help me out on how to accomplish the Digest case?

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