SOLIDUI: The logout button on the appbar should be replaced with login button if the user is not logged in

[tonypioneer]

Description

The logout button on the appbar should be replaced with login button if the user is not logged in.

When logging in again, regardless of whether the user enters via the logged in status on the status bar or via the login button on the appbar, they will be redirected to a new default login page with the title Solid App, instead of being redirected back to the app’s Solid login page.

Why

This will prevent the issue that when the user is not logged in, and he/she can still try to log out from the app.

Closing Criteria

Checklist for closing the issue:

• No errors from make prep
• All tests pass make qtest
• The logout button on the appbar is replaced with login button if the user is not logged in.
• When logging in again, regardless of whether the user enters via the logged in status on the status bar or via the login button on the appbar, they can be redirected back to the app’s Solid login page.

[tonypioneer]

If the user is logged in, the button on the appbar is logout button.

If the user is logged out, the button on the appbar is login button.