dovecot service: add sendmail_path

Changed files
+1
nixos
modules
services
+1
nixos/modules/services/mail/dovecot.nix
···
''
base_dir = ${baseDir}
protocols = ${concatStringsSep " " cfg.protocols}
+
sendmail_path = /var/setuid-wrappers/sendmail
''
(if isNull cfg.sslServerCert then ''