* refactored scripts located under `target/bin/`
The scripts under `target/bin/` now use the new log and I replaced some
`""` with `''` on the way. The functionality stays the same, this mostly
style and log.
* corrected fail2ban (script and tests)
* corrected OpenDKIM log output in tests
* reverted (some) changes to `sedfile`
Moreover, a few messages for BATS were streamlined and a regression in
the linting script reverted.
* apple PR feedback
* improve log output from `fail2ban` script
The new output has a single, clear message with the '[ ERROR ] '
prefix, and then output that explains the error afterwards. This is
coherent with the logging style which should be used while providing
more information than just a single line about IPTables not functioning.
* simplified `setquota` script
* consistently named the `__usage` function
Before, scripts located under `target/bin/` were using `usage` or
`__usage`. Now, they're using `__usage` as they should.
* improved `sedfile`
With `sedfile`, we cannot use the helper functions in a nice way because
it is used early in the Dockerfile at a stage where the helper scripts
are not yet copied. The script has been adjusted to be canonical with
all the other scripts under `target/bin/`.
* fixed tests
* removed `__usage` from places where it does not belong
`__usage` is to be used on wrong user input, not on other failures as
well. This was fixed in `delquota` and `setquota`.
* apply PR review feedback
* added new `_log` function
With `_log`, the `_notify` method wa rendered obsolete. `_notify` was
not completely removed due to test failures in `check-for-changes.sh`.
The new `_log` function properly uses log levels such as `trace`,
`debug`, `info`, `warn` and `error`. It provides a cleaner solution
and renders `DMS_DEBUG` obsolete too (as only `_notify` depends on it).
* converted all helper script to new `_log` function
* converted all startup stacks to new `log` function
* `start-mailserver.sh` now uses new `_log` function
* final test and misc small script adjustments
* updated documentation