* refactored `check-for-changes.sh`
I refactored `check-for-changes.sh` and used the new log. `_notify` can
therefore be deleted as it is used no more.
I opted to source `/etc/dms-settings` as a whole to
future-proof the script. When the DNS adjustments PRs (that do not exist
by now but will exit in the future) are done, we can then remove
`_obtain_hostname_and_domainname` because we're already writing the
variables to `/etc/dms-settings`. I left instructions in the script in
the form of TODO comments.
Because we now log the date for all messages of the changedetector, we
need to `tail` a bit more log than before.
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