login: Malformed login URL arg breaks login, sh and sync

[Russtopia]

As a naive user I tried

coder login localhost:8080
coder login master.cdr.dev

The browser auto-launch of the login URL is malformed in the above cases (and the text on terminal if autolaunch fails)

If I specify the full URL eg.
coder login http://localhost:8080

the URL generated is correct, and subsequent coder sh and coder sync ops work.

Recommend adding logic to prepend http:// if not specified by the user.

[wbobeirne]

I think it'd be better to have them specify a full URI, since it could be https and they may not have redirects setup.

[Russtopia]

I think it'd be better to have them specify a full URI, since it could be https and they may not have redirects setup.

Sorry, didn't see this until after I merged, but that's what I ended up doing. It doesn't try to fix up the incomplete URI -- it rejects and and the help/usage is updated to show an example. I can improve on it more if you think it should be more explicit.