Logout feature

[soxofaan]

idea from #249:

add logout (or something similar) feature to remove all local storage/caching of configs, access/refresh tokens
to be used on a shared computer and user wants to be sure that no sensitive data is left behind

[m-mohr]

fyi: OIDC also has a logout endpoint/functionality (see e.g. the Web Editor logout), which you'd want to call on logout to discard tokens also on server-side (IP).