Nginx variable equivalent of: $scheme://$host:$port
The variables $scheme://$host:$server_port are all supported by Nginx and are documented here.
However, you don't necessarily need to use them, as Nginx automatically provides the missing components.
For example, the statement:
return 301 /login;
will use the same scheme, host and port as the original request by default, unless this behaviour is explicitly overridden by directives such as absolute_redirect,
port_in_redirect, or server_name_in_redirect.