Connect as a named user when creating the first API key

[nblumhardt]

Fixes #188

This enables:

seqcli apikey create -t First --token="yourtokenhere" --connect-username=admin --connect-password=password --permissions="Read,Write,Setup"

Some form of testing still outstanding. ✔️

[nblumhardt]

Alrighty, ready to go!

I think the main thing that warrants explanation is the choice of --connect-username= and --connect-password= in preference over --username and --password: we have several API endpoints that take usernames and passwords as arguments.

In those cases we may still at some point want to separately control the username and password used when making the connection to the API.

E.g. if we ended up supporting username/password auth everywhere, you'd hit this conflict when creating another user, or when configuring credentials for a NuGet feed.

[codedevote]

Wow, great news, Nick. I was looking at the tests yesterday and came back here to ask whether I can try to write an end-to-end test, just to find that you already finished it 🥇 If there is still anything I can help with, feel free to reach out.

[nblumhardt]

Thanks, Florian 👍