Implement a disconnected login flow

[charlieegan3]

Fixes #50.

Test this with:

go run main.go auth login --disconnected

Signed-off-by: Charlie Egan charlieegan3@users.noreply.github.com

[irbekrm]

Thanks Charlie!

Have you tested it?
I tried running go run main.go auth login --disconnected from my laptop and got this output:

irbe@jsctl$ go run main.go auth login --disconnected
Navigate to the URL below to login:
https://auth.jetstack.io/authorize?access_type=offline&audience=https%3A%2F%2Fpreflight.jetstack.io%2Fapi%2Fv1&client_id=jmQwDGl86WAevq6K6zZo6hJ4WUvp14yD&redirect_uri=http%3A%2F%2Flocalhost%3A9999%2Foauth%2Fcallback&response_type=code&scope=openid+profile+offline_access&state=0a3464bd-fa67-4063-8822-1b97a8ba19b4
Enter the URL you were redirected to (http://localhost:9999...) and press enter

I then tried entering the https://auth.jetstack.io/authorize?access_type=offline... URL from my phone, but got an error:

(sorry for the mega image, just wanted to show the URL as well)

[irbekrm]

Also, might be good to allow a user to Ctrl-C out of the command whilst it's hanging waiting for user input, perhaps a matter of passing in context, I've not looked at the code yet.

[charlieegan3]

I have tested this and it does work. The URL to enter is the localhost9999 one after the redirect completes. The server isn't running so the connection_refused error is expected.

I tried to explain this in the message:

Enter the URL you were redirected to (http://localhost:9999...) and press enter

I do however need to make sure that ctrl+C works so I'll do that now.

[charlieegan3]

I have added the interrupt in 98b1cf9

[irbekrm]

I have tested this and it does work. The URL to enter is the localhost9999 one after the redirect completes. The server isn't running so the connection_refused error is expected.

Cool I think I have misunderstood it, I assumed that the use case is enterprise VPN setup where folks might not be able to access Jetstack Secure and their cluster from the same machine. What is the use case then and how can this PR be tested?

[charlieegan3]

This can be tested on a normal machine / env.

First, run:

go run main.go auth login --disconnected

Visit the URL on any device. Phone or even the same machine.

Copy the localhost:9999 URL into the terminal window.

Press enter.

Verify that you are logged in.

[charlieegan3]

waiting for feedback on #50 (comment) before merging

[charlieegan3]

We've had some acknowledgment that this ought to work ok now. @irbekrm can you ✅ ?

[irbekrm]

Thanks for working on this Charlie

/lgtm

[charlieegan3]

Thanks Irbe.