App does not validate server URLs

[hugodutka]

By mistake, instead of prefixing the server URL with "https://", I typed "https:/". The app didn't show an error initially, but after signing in and enabling Coder VPN, the app failed to fetch workspaces with a confusing error:

It took me a couple of minutes to figure out what's wrong. It'd be great to do basic validation of user input.

[ethanndickson]

This is super weird, for whatever reason a GET request to https:/dev.coder.com is working (as we validate the token against /api/v2/users/me on the sign in screen, in Swift code), as is the download, but the error you're seeing is from the Go code. Will investigate.