GTFS-RT converter: switch to newly imported GTFS automatically

[derhuerst]

Currently, new GTFS datasets get imported automatically:

gtfs-rt-infrastructure/playbooks/gtfs-rt-converters.yml

Lines 107 to 114 in b08dd86

	- name: set up GTFS import cron job
	ansible.builtin.cron:
	name: 'gtfs-rt-feed: GTFS import'
	user: root # todo: use `www-data` instead?
	cron_file: gtfs-rt-feed-gtfs-import
	job: '{{ gtfs_rt_feed_import_cmd }}'
	# every hour
	minute: '3'

gtfs-rt-infrastructure/group_vars/gtfs_rt_converter.yml

Lines 29 to 32 in b08dd86

	# This command imports the GTFS data into a database. It then writes a systemd override config file setting $PGDATABASE.
	# We assume that it is executed using `sh`.
	# todo: make $GTFS_IMPORTER_DB_PREFIX configurable
	gtfs_rt_feed_import_cmd: "export PGUSER=postgres PGPASSWORD='{{ postgresql_postgres_password }}' PGDATABASE='{{ gtfs_rt_feed_gtfs_importer_db }}' && env GTFS_DOWNLOAD_USER_AGENT='{{ gtfs_rt_feed_gtfs_download_user_agent }}' {{ gtfs_rt_feed_dir }}/import.sh --docker && echo \"[Service]\\nEnvironment=PGDATABASE=$(psql -q --csv -t -h localhost -c 'SELECT db_name FROM latest_import')\"| sponge /etc/systemd/system/gtfs-rt-feed.service.d/pgdatabase.conf"

However, gtfs-rt-feed.service needs to be restarted afterwards to use the new data.