re-enable running the CI in pull requests, but not concurrently

[missytake]

Fix #246

Fix #217

I documented the sysadmin side in https://github.com/deltachat/sysadmin/commit/b1fbedc2fd5982d58584a5c6499368018ca68ee1

It would be nice if we could make sure that the offline tests and formatting checks don't make the CI stop if they fail; because then it doesn't get to the step where it can restore the ACME and DKIM state, and we lose some private certs on the server.

[missytake]

The CI fails because of #217

[link2xt]

Failure is not related do opendkim, postfix log starts like this:

Mar 28 19:10:34 staging systemd[1]: Starting postfix@-.service - Postfix Mail Transport Agent (instance -)...
Mar 28 19:10:35 staging postfix/postfix-script[3394]: starting the Postfix mail system
Mar 28 19:10:35 staging postfix/master[3396]: daemon started -- version 3.7.10, configuration /etc/postfix
Mar 28 19:10:35 staging systemd[1]: Started postfix@-.service - Postfix Mail Transport Agent (instance -).
Mar 28 19:12:37 staging systemd[1]: Stopping postfix@-.service - Postfix Mail Transport Agent (instance -)...
Mar 28 19:12:38 staging postfix/postfix-script[8073]: stopping the Postfix mail system
Mar 28 19:12:38 staging systemd[1]: postfix@-.service: Deactivated successfully.
Mar 28 19:12:38 staging systemd[1]: Stopped postfix@-.service - Postfix Mail Transport Agent (instance -).
Mar 28 19:12:38 staging systemd[1]: Starting postfix@-.service - Postfix Mail Transport Agent (instance -)...
Mar 28 19:12:38 staging postfix/postfix-script[8363]: starting the Postfix mail system
Mar 28 19:12:38 staging postfix/master[8365]: daemon started -- version 3.7.10, configuration /etc/postfix
Mar 28 19:12:38 staging systemd[1]: Started postfix@-.service - Postfix Mail Transport Agent (instance -).
Mar 28 19:12:41 staging postfix/smtps/smtpd[8391]: connect from localhost[127.0.0.1]
Mar 28 19:12:41 staging postfix/smtps/smtpd[8391]: warning: SASL: Connect to Dovecot auth socket 'private/auth' failed: No such file or directory
Mar 28 19:12:41 staging postfix/smtps/smtpd[8391]: fatal: no SASL authentication mechanisms
Mar 28 19:12:42 staging postfix/master[8365]: warning: process /usr/lib/postfix/sbin/smtpd pid 8391 exit status 1
Mar 28 19:12:42 staging postfix/master[8365]: warning: /usr/lib/postfix/sbin/smtpd: bad command startup -- throttling
Mar 28 19:12:42 staging postfix/submission/smtpd[8469]: connect from localhost[127.0.0.1]
Mar 28 19:12:42 staging postfix/submission/smtpd[8469]: warning: SASL: Connect to Dovecot auth socket 'private/auth' failed: No such file or directory
Mar 28 19:12:42 staging postfix/submission/smtpd[8469]: fatal: no SASL authentication mechanisms
Mar 28 19:12:43 staging postfix/master[8365]: warning: process /usr/lib/postfix/sbin/smtpd pid 8469 exit status 1
Mar 28 19:12:43 staging postfix/master[8365]: warning: /usr/lib/postfix/sbin/smtpd: bad command startup -- throttling
Mar 28 19:13:17 staging postfix/smtpd[8748]: connect from unknown[40.76.117.196]
Mar 28 19:13:18 staging postfix/smtpd[8748]: lost connection after VRFY from unknown[40.76.117.196]
Mar 28 19:13:18 staging postfix/smtpd[8748]: disconnect from unknown[40.76.117.196] vrfy=4 commands=4
Mar 28 19:13:42 staging postfix/smtps/smtpd[8815]: connect from localhost[127.0.0.1]
Mar 28 19:13:42 staging postfix/smtps/smtpd[8816]: connect from unknown[40.76.117.196]
Mar 28 19:13:42 staging postfix/smtps/smtpd[8815]: disconnect from localhost[127.0.0.1] ehlo=1 auth=1 quit=1 commands=3

The problem is that /var/spool/postfix/private/auth is created too late:

root@staging:~# stat /var/spool/postfix/private/auth 
  File: /var/spool/postfix/private/auth
  Size: 0         	Blocks: 0          IO Block: 4096   socket
Device: 8,1	Inode: 128643      Links: 1
Access: (0660/srw-rw----)  Uid: (  995/ postfix)   Gid: (  994/ postfix)
Access: 2024-03-28 19:13:42.295130430 +0000
Modify: 2024-03-28 19:12:43.143992693 +0000
Change: 2024-03-28 19:12:43.143992693 +0000
 Birth: 2024-03-28 19:12:43.143992693 +0000

We need to ensure somehow that Dovecot creates socket before we start Postfix.

We can try to create /etc/systemd/system/postfix.service.d/service.conf and add Requires=dovecot.service into [Unit] section or symlink dovecot.service into /etc/systemd/system/postfix.service.requires/dovecot.service.

[link2xt]

Works after reordering Dovecot before Postfix.