* major refactoring for setup.sh (#1590)
* `set -u` stopped dkim generation from defaulting
* changed to bash and implemented simple error logging
* fixed $VOLUME not being set and refactored README as well due to markdownlint showing (valid) complaints
* setup.sh more consistent with braces, return codes, un-setting of variables and error reports and (importantly) test
Previously, only postfix-relaymap.cf and postfix-accounts.cf would be
used to populate the relayhost_map file.
Now, also use postfix-virtual.cf when present. To me, there is nothing
absurd about sending mail "From:" a virtual account (or more
specifically its domain) so it makes sense that when a $RELAY_HOST is
defined it should be used for virtual accounts as well.
check-for-changes.sh did not have a special case to handle lines in
postfix-relaymap.cf consisting of only a domain (indicating that said
domain should never be relayed). This case is handled by
start-mailserver.sh so when such a line existed, things would work well
until a config file update was detected by check-for-changes.sh. After
that, the generated relayhost_map file would be corrupted.
Fixed by factoring a 'populate_relayhost_map' function out of
start-mailserver.sh and into helper_functions.sh and reusing it in
check-for-changes.sh.
Note: There are certainly quite a few more pieces of code that could be
refactored in a similar fashion.
Note2: check-for-changes.sh would previously never update the
relayhost_map file when $ENABLE_LDAP was set to 1. I don't think this
was intended —there is after all no such condition in
start-mailserver.sh— and so this condition no longer applies.
If a change to one of the tracked files happened soon after (<1 second?)
a previously detected change, it could end up going undetected. In
particular, this could cause integration tests to fail (see next
commits).
Fixed by computing the new checksum file _before_ checking for changes.
Will extract certificates from acme.json as written by traefik for usage in dovecot and postfix.
Also watches acme.json for changes. For this to work the file has to be mounted/present at `/etc/letsencrypt/acme.json`
