Virtual path in URL when running phoenix locally

See whenever you run a phoenix app locally, the URL is always something like:

http://localhost:4100

where 4100 is the port number I configured in my dev.exs

How can I make it so that the URL has some dummy virtual paths in it. For example:

http://localhost:4100/arch/myapp

The reason I want to do this is because in our company when we deploy our apps to production they have to be accessed through a proxy server. The proxy server maps a friendlier URL (without a port number) to the linux vm that is running the actual application. For example:

http://proxy.mycompany.com/arch/myapp => http://vmlinuxprd1:8080

The problem I am facing is that my app runs fine locally and all the URLS are resolved correctly. But fails in production.

I want to be able to simulate this problem locally so I can test my application when the URL has a few dummy virtual directories in the path. That way I am guaranteed that it will run fine in production by resolving all the relative URLs correctly in production.

Thank you!