how do I configure nginx to send user ip in response headers

I have an nginx server I installed on ubuntu 20.04 server. I'm trying to get the user IP address but nginx doesn't seem to be configured to pass it. when looking at access logs /var/log/nginx/access.log - I can see the correct IP address.

I'm testing this issue with a basic flask program below:

from flask import Flask,jsonify,request

app = Flask (__name__)
@app.route('/')
def home():
    return jsonify({"request.remote_addr" : request.remote_addr })
if __name__ == "__main__":
    app.run(host='0.0.0.0')

nginx configuration file minus SSL lines for this is:

server{
     server_name test.testweb.com;
     location / {
         proxy_pass http://unix:/home/flask/test/test.sock;
     }
}

when I run this with flask dev server, it works as expected. when I run it on nginx/gunicorn, I get an empty string for IP address.
what configuration is required on nginx to pass the user IP address to the server?