[Documentation] Provide example of nginx reverse-proxy with context path

[cowwoc]

The documentation at https://help.sonatype.com/en/docker-repository-reverse-proxy-strategies.html#nginx-host-mapping-reverse-proxy-example works well when nexus is running at the root of a server, but if there is a context path then it will not work.

The suggested configuration reads:

Docker /v2 and /v1 (for search) requests

location /v2 {
proxy_set_header Host $host:$server_port;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto "https";
proxy_pass http://nexus.example.com:8081/repository/docker-repo/$request_uri;
}
location /v1 {
proxy_set_header Host $host:$server_port;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto "https";
proxy_pass http://nexus.example.com:8081/repository/docker-repo/$request_uri;
}

Regular Nexus requests

location / {
proxy_set_header Host $host:$server_port;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto "https";
proxy_pass http://nexus.example.com:8081;
}

But if you have a context path /binaries with a docker repository called docker-proxy then the configuration needs to be:

Docker /v2 and /v1 (for search) requests

location /v2/binaries {
rewrite ^/v2/binaries/repository/docker-proxy/(.*)$ /binaries/repository/docker-proxy/v2/$1 break;

 proxy_set_header Host $host:$server_port;
 proxy_set_header X-Real-IP $remote_addr;
 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 proxy_set_header X-Forwarded-Proto "https";
 proxy_pass http://nexus.example.com:8081/;

}
location /v1/binaries {
rewrite ^/v1/binaries/repository/docker-proxy/(.*)$ /binaries/repository/docker-proxy/v1/$1 break;

 proxy_set_header Host $host:$server_port;
 proxy_set_header X-Real-IP $remote_addr;
 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 proxy_set_header X-Forwarded-Proto "https";
 proxy_pass http://nexus.example.com:8081/;

}

Regular Nexus requests

location /binaries {
proxy_set_header Host $host:$server_port;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto "https";
proxy_pass http://nexus.example.com:8081/binaries;
}

Please update the documentation to discuss this case. It is not intuitive to go from the existing example to the required configuration. Thank you.