Bug#972527: Support arbitrary arguments in /etc/default/dnss

[Florian Schlichting]

Control: severity 972527 important

Dear dnss maintainers,

> /lib/systemd/system/dnss.service uses curly braces with
> ${MONITORING_FLAG} and ${MODE_FLAGS}, which means each one can only
> have a single argument in it.

please please fix this? It just needs dnss.service to not use curly braces:

    EnvironmentFile=-/etc/default/dnss
    ExecStart=/usr/bin/dnss \
            --dns_listen_addr=systemd \
            $MONITORING_FLAG \
            $MODE_FLAGS

This makes it possible to set more than one flag in MODE_FLAGS in
/etc/default/dnss, for example (and mentioned in README.md):

    MODE_FLAGS='-enable_dns_to_https 
-https_upstream="https://1.1.1.1/dns-query";'

This fix would be particularly helpful because the error mesage will be
confusing unless one already knows about this problem:

    systemd[1]: dnss.service: Main process exited, code=exited, 
status=2/INVALIDARGUMENT
    flag provided but not defined: -enable_dns_to_https -https_upstream

(see also merge request !1 on salsa)

thanks,
Florian