How to define a location by a string in URL using NGINX

I have the URL:

https://mysitedomain:8443/app/visualize?security_tenant=global#/edit/9e5fc420-89cd-11ec-b13a-ddde90ebb494?embed=true&_g=(filters%3A!()%2CrefreshInterval%3A(pause%3A!t%2Cvalue%3A0)%2Ctime%3A(from%3Anow-1y%2Cto%3Anow))

I need to permit it go to the proxy_pass if the string "embed=true" are present in the URL.

I did alot of tries but no success, i think my regex is not working, I have try so many regexes that I am actually lost.

There is my configuration:

    location ~ embed$ {

      proxy_set_header Accept-Encoding "";
      proxy_redirect off;
      proxy_buffering off;
      proxy_http_version 1.1;
      proxy_set_header Authorization "Basic YWRtaW46Y3WRaW4=";
      proxy_set_header Connection "Keep-Alive";
      proxy_set_header Proxy-Connection "Keep-Alive";
      proxy_pass https://thesite;
   }

Looking at Debug of nginx, looks like nginx are not getting all the URL strings, and just the prefix of it:

2022/03/17 23:11:24 [debug] 35347#0: *1 http request line: "GET /app/visualize?security_tenant=global HTTP/1.1"
2022/03/17 23:11:24 [debug] 35347#0: *1 http uri: "/app/visualize"
2022/03/17 23:11:24 [debug] 35347#0: *1 http args: "security_tenant=global"
2022/03/17 23:11:24 [debug] 35347#0: *1 http exten: ""