Kopano spamd, Bugfixes (#17)

* Add container for kopano-spamd
* Authenticate version requests if needed
* Fix building of z-push for 'supported' base image
* Install kopano-spamd package by default
* Smaller fixes for kopano-spamd
* Fix missing file header
* simplify netrc usage

core/Dockerfile

@@ -47,7 +47,7 @@ RUN --mount=type=secret,id=repocred,target=/etc/apt/auth.conf.d/kopano.conf \
     apt-get update && \
     set -x && \
     apt-get -o Debug::pkgProblemResolver=true install --no-install-recommends -y \
-        kopano-server-packages \
+        kopano-server-packages kopano-spamd \
         ${ADDITIONAL_KOPANO_PACKAGES} \
         && \
     coreversion=$(dpkg-query --showformat='${Version}' --show kopano-server) && \