Reapply "nixos/dovecot: improve and harden systemd unit"

This reverts commit a794031c597bd8a1898a1305b70952508e2d3612.

With the following additions:

Allow `CAP_KILL`, so the dovecot master process may interrupt its child
processes.

Allow new privileges, so dovecot and call the setuid sendmail executable.

Allow AF_NETLINK sockets, so dovecot sieve handling can use the
getifaddrs syscall.

Finally, we now asssert, that no options are set on the legacy dovecot2
systemd unit name, to make the user aware they need to update their
overrides.

0 files changed, 0 insertions, 0 deletions