Sign-out button

[hvbish]

It would be good to add a button that lets you sign out of your Spotify account. Currently, if a user wants to sign out or use the Wayfinder with another account, they have to delete browser cookies manually or use incognito mode.

[stevenstetzler]

This could be implemented easily I think...

Currently, the Flask app will check if a user is logged in by calling the check_logged_in() function before returning the visualization: https://github.com/The-Wayfinder-Society/wayfinder-app/blob/master/main.py#L279-L281

The check_logged_in() function inspects the browser cookies and will guide the user to the /login or /refresh page based on the status of the access tokens found: https://github.com/The-Wayfinder-Society/wayfinder-app/blob/master/main.py#L90-L113

I think we can create a new function logout() that would clear these cookies and redirect the user to the homepage like so:

@app.route("/logout")
def logout():
    response = redirect(url_for("index"))
    response.set_cookie("SpotifyUserAccessToken", "", expires=0)
    response.set_cookie("SpotifyUserRefreshToken", "", expires=0)
    return response

in main.py and then add a new link to the Viz page (templates/viz.html) or main page (templates/index.html) like so:

<a href="/logout">Sign Out</a>