Handle GitLab access token mandatory expiration

GitLab recently introduced a maximum lifetime for all access tokens. The change is discussed in a blog post from last October. Most importantly:

As of the 16.0 milestone (May 2023), we applied an expiration date of May 14, 2024, to any personal, group, or project access token that previously didn't have one.

We should provide a convenient way of dealing with token renewal for the many tokens used across this instance which are now set to expire soon.

Unfortunately, it seems like we're more or less to our own devices to figure out which tokens/projects are affected by this change.