Add logout functionality and improve login/logout design

[steff456]

Fixes #247.

Description

This pull request:

• adds the functionality for log out
• removes the login icon
• follows the design described in comment ENH - Improve log in/out functionality #247 (comment)
• updates documentation for the logout url option

Pull request checklist

• Did you test this change locally?
• Did you update the documentaion (if required)?
• Did you add/update relevant tests for this change (if required)?

Additional information

log.mp4

[pierrotsmnrd]

I have tested this PR, with the latest version of conda-store.

• The login works ✅
• but the logout doesn't, it keeps me logged in ❌

I have tried with the old ui : I was able to log out, which leads me to think the problem is on the UI side.

[steff456]

@pierrotsmnrd can you please upload a video of what you are seeing? The logout is working on my side 🤨

[pierrotsmnrd]

Ok, the problem was on my end. I got a CORS error because of a misconfiguration in my conda-store instance.

Good to go ! :)