Docker: Add monolog configuration when running as a container

This will let the logs go to stdout when running as a container, which
is the Docker way to send logs

config/packages/prod/monolog.yaml.docker

@@ -0,0 +1,15 @@
+monolog:
+    handlers:
+        prod-signaler:
+            type: fingers_crossed
+            action_level: ERROR
+            passthru_level: NOTICE # this means that all message of level NOTICE or higher are always logged
+            handler: main_syslog
+            bubble: false # if we handle it, nothing else should
+        main_syslog:
+            type: stream
+            path: "php://stderr"
+            formatter: surfnet_stepup.monolog.json_formatter
+        console:
+            type: console
+            process_psr_3_messages: false

docker/Dockerfile.prod

@@ -6,6 +6,7 @@ RUN tar -xvjf /tmp/*.tar.bz2 -C /var/www/html/ && \
 # Add the application configuration files
 RUN cp .env.dist .env
 RUN cp config/packages/parameters.yml.dist config/packages/parameters.yml
+COPY config/packages/prod/monolog.yaml.docker config/packages/prod/monolog.yaml
 
 # Add the config files for Apache2
 RUN rm -rf /etc/apache2/sites-enabled/*