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

docker-compose.yml

@@ -195,6 +195,7 @@ services:
       - db
       - ldap
       - kopano_ssl
+      - kopano_konnect
     ports:
       - ${KOPANOPORT:-236}:236
       - ${KOPANOSPORT:-237}:237
@@ -309,7 +310,7 @@ services:
       - web-net
 
   kopano_kdav:
-    image: ${docker_repo:?err}/kopano_kdav:${KDAV_VERSION:-latest}
+    image: ${docker_repo:-zokradonh}/kopano_kdav:${KDAV_VERSION:-latest}
     hostname: kopano_kdav
     container_name: ${COMPOSE_PROJECT_NAME}_kdav
     depends_on:
@@ -441,6 +442,7 @@ services:
      - kopanosocket/:/run/kopano
     depends_on:
      - kopano_ssl
+     - web
     environment:
      - FQDN=${FQDN}
      - allow_client_guests=yes
@@ -493,6 +495,27 @@ services:
     networks:
      - web-net
 
+  kopano_scheduler:
+    image: ${docker_repo:-zokradonh}/kopano_scheduler:${SCHEDULER_VERSION:-latest}
+    container_name: kopano_scheduler
+    restart: always
+    networks:
+      - kopano-net
+      - ldap-net
+      - web-net
+    depends_on:
+      - kopano_server
+      - kopano_zpush
+    environment:
+      - TZ=${TZ}
+      - CRON_KOPANOUSERS=10 * * * * docker exec kopano_server kopano-cli --sync
+      - CRON_ZPUSHGAB=0 22 * * * docker exec kopano_zpush z-push-gabsync -a sync
+      - CRONDELAYED_KBACKUP=30 1 * * * docker run --rm -it zokradonh/kopano_utils kopano-backup -h
+    env_file:
+      - ldap.env
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
 volumes:
   web:
   ldap: