wip: Implement a scheduler to run recurring tasks (such as z-push-gabsync) (#123)

* add scheduler container for gabsync
Adds a general scheduler container to trigger tasks within containers.
Also adds gabsync to zpush image
* make scheduler dynamic
execute each cron job once at startup to see if they would succeed
* remove services scripts from core container (now is part of the scheduler)
* add "CRONDELAY" for tasks that should not be executed at startup
* add documentation
* clear out crontab at startup

zpush/Dockerfile

@@ -45,6 +45,7 @@ RUN \
         crudini \
         z-push-kopano \
         z-push-config-apache \
+        z-push-kopano-gabsync \
         ca-certificates \
         ${ADDITIONAL_KOPANO_PACKAGES} \
     && rm -rf /var/cache/apt /var/lib/apt/lists
@@ -73,6 +74,12 @@ RUN sed -i -e 's/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen && \
     mkdir -p /var/lib/z-push /var/log/z-push && \
     chown www-data:www-data /var/lib/z-push /var/log/z-push
 
+# Patch Gabsync to make it work
+# See https://jira.z-hub.io/browse/ZP-1463
+# https://forum.kopano.io/topic/1928/8-7-80-missing-php-files-in-php-mapi-deb-package-ubuntu-16-04
+# can be removed once gabsync is fixed - should not hurt
+RUN sed -i -e "s/set_include_path(get_include_path() . PATH_SEPARATOR . BASE_PATH_CLI);/define('PATH_TO_ZPUSH', '..\/..\/backend\/kopano\/');\n    set_include_path(get_include_path() . PATH_SEPARATOR . BASE_PATH_CLI . PATH_SEPARATOR . BASE_PATH_CLI . PATH_TO_ZPUSH);/" /usr/share/z-push/tools/gab-sync/gab-sync.php
+
 VOLUME /var/lib/z-push/
 
 EXPOSE 80/tcp

zpush/start.sh

@@ -30,6 +30,9 @@ echo "Configuring Z-Push for use behind a reverse proxy"
 sed -e "s#define([\"']USE_CUSTOM_REMOTE_IP_HEADER[\"'],\s*false)#define('USE_CUSTOM_REMOTE_IP_HEADER', 'HTTP_X_FORWARDED_FOR')#" \
     -i /etc/z-push/z-push.conf.php
 
+sed -e "s#define([\"']USERNAME[\"'],\s*'')#define('USERNAME', 'SYSTEM')#" \
+    -i /etc/z-push/gabsync.conf.php
+
 echo "Ensure config ownership"
 chown -R www-data:www-data /run/sessions