Nginx reverse proxy behind squid proxy

I have to create a reverse proxy for my internal services to call third party service. some of our third party service providers has a squid or any http proxy with authentication to reach out their services.

For simulation I create a reversproxy with name "reverseproxy" that expose port 85, we expect if customer browse http://localhost:85/httpsbin2/api/get then all traffic sent to https://httpbin.org/get throw an sqid proxy that we named it "squidproxy" and receive the response. docker-compose dile and nginx config file below

docker-compose.yml

version: '2'

networks:
  isb-network:
      driver: bridge
  no-internet:
    driver: bridge
    internal: true
services: 
  reverseperoxy:
    image: nginx
    container_name: reverseproxy
    volumes:    
      - ./nginx/conf.d:/etc/nginx/conf.d/
      - ./nginx/log:/var/log/nginx
    networks:
      - isb-network
    ports:
      - '85:80'

  squidproxy:
    image: robhaswell/squid-authenticated
    container_name: squidproxy
    environment:
      - SQUID_USERNAME=foo
      - SQUID_PASSWORD=bar
    networks:
      - isb-network
    ports:
      - '3128:3128'
    volumes:
      - ./squid/squid.conf:/etc/squid/squid.conf
      - ./squid/passwords:/etc/squid/passwords
      - ./squid/logs:/usr/local/squid/var/logs

and nginx config file

default.conf

server {
    listen       80;
    listen  [::]:80;
    server_name  localhost reverseproxy httpbin2.org "";
    
    rewrite_log on;
    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }

    location /httpsbin/api/ {# only for test, this section work 
      proxy_pass https://httpbin.org/;
    }

    location /httpsbin2/api/ {# we have problem here 
        proxy_pass http://squidproxy:3128/;
        proxy_set_header Host httpbin.org;
        proxy_set_header X-Forwarded-For httpbin.org;
        proxy_set_header Authorization "Basic Zm9vOmJhcg==";
        proxy_redirect http://localhost:85/httpsbin2/api http://httpbin.org;
    }
}

I test squid proxy with my browser and it works fine and i think the problem is with Nginx config

Problem: when I call http://localhost:85/httpsbin2/api/get it redirected to squid but squid received only /get not http://httpbin.org/get and I see below error from squid:

Invalid URL

Some aspect of the requested URL is incorrect.

Some possible problems are:

Missing or incorrect access protocol (should be http:// or similar)

Missing hostname

Illegal double-escape in the URL-Path

Illegal character in hostname; underscores are not allowed.