docker: add a cron docker service

This adds busybox to the php-fpm image and creates a separate container
via docker-compose which starts crond and calls our cron command
every 5 minutes.

This makes sure our cron jobs are called during development, just like
on a production server.

docker-dev/docker-compose.yml

@@ -39,6 +39,18 @@ services:
       - ..:/application
       - ./php-fpm/php-ini-overrides.ini:/etc/php/7.4/cli/conf.d/99-overrides.ini
 
+  cron:
+    build:
+      context: php-fpm
+    depends_on:
+      - mariadb
+      - redis
+    working_dir: /application
+    entrypoint: /cron.sh
+    volumes:
+      - ..:/application
+      - ./php-fpm/php-ini-overrides.ini:/etc/php/7.4/cli/conf.d/99-overrides.ini
+
   redis:
     image: "redis"
     entrypoint: redis-server --save 60 1 --loglevel warning

docker-dev/php-fpm/Dockerfile

@@ -6,7 +6,9 @@ ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get update \
     && apt-get -y --no-install-recommends install \
         ca-certificates \
+        tini \
         libldap-common \
+        busybox-static \
         curl \
         unzip \
         sudo \
@@ -36,6 +38,11 @@ RUN apt-get update \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
+# Cron setup, run every 5 minutes
+RUN mkdir -p /var/spool/cron/crontabs; \
+    echo '*/5 * * * * php -f /application/bin/console dbp:relay:core:cron' > /var/spool/cron/crontabs/user
+COPY cron.sh /
+
 STOPSIGNAL SIGQUIT
 
 ARG UID

docker-dev/php-fpm/cron.sh

+#!/bin/sh
+set -eu
+
+exec tini -- sudo busybox crond -f -l 0 -L /dev/stdout
\ No newline at end of file