Configurable uid gid (#9)

* allow to specify uid and gid for kopano
* Set default value of GID/UID to keep compatibility with existing containers

base/Dockerfile

@@ -8,6 +8,9 @@ ARG KOPANO_CORE_VERSION=newest
 ARG KOPANO_REPOSITORY_FLAGS="trusted=yes"
 ARG RELEASE_KEY_DOWNLOAD=0
 
+ARG KOPANO_UID=999
+ARG KOPANO_GID=999
+
 ENV \
     BASE_VERSION=1.3.0 \
     DEBUG="" \
@@ -47,6 +50,10 @@ RUN apt-get update && \
         curl -s -S -o - "${KOPANO_CORE_REPOSITORY_URL}/Release.key" | apt-key add -; \
     fi
 
+# Create kopano user and group
+RUN groupadd --system --gid ${KOPANO_GID} kopano
+RUN useradd --system --shell /usr/sbin/nologin --home /var/lib/kopano --gid ${KOPANO_GID} --uid ${KOPANO_UID} kopano
+
 ENV DOCKERIZE_VERSION v0.11.0
 RUN curl -sfL https://github.com/powerman/dockerize/releases/download/"$DOCKERIZE_VERSION"/dockerize-"$(uname -s)"-"$(uname -m)" \
     | install /dev/stdin /usr/local/bin/dockerize && \