feat(worker): load config using shared helpers

BREAKING CHANGE: The worker `RMQ_CONFIG_FILE` environement variable has
been renamed to `LIBRETIME_CONFIG_FILEPATH`. In addition the systemd
working directory for the worker has changed from `/srv/airtime` to
`/var/lib/libretime/worker`.

worker/libretime_worker/celeryconfig.py

@@ -1,43 +0,0 @@
-import os
-
-from configobj import ConfigObj
-from kombu import Exchange, Queue
-
-# Get the broker string from airtime.conf
-RMQ_CONFIG_SECTION = "rabbitmq"
-
-
-def get_rmq_broker():
-    rmq_config = ConfigObj(os.environ["RMQ_CONFIG_FILE"])
-    rmq_settings = parse_rmq_config(rmq_config)
-    return "amqp://{username}:{password}@{host}:{port}/{vhost}".format(**rmq_settings)
-
-
-def parse_rmq_config(rmq_config):
-    return {
-        "host": rmq_config[RMQ_CONFIG_SECTION]["host"],
-        "port": rmq_config[RMQ_CONFIG_SECTION]["port"],
-        "username": rmq_config[RMQ_CONFIG_SECTION]["user"],
-        "password": rmq_config[RMQ_CONFIG_SECTION]["password"],
-        "vhost": rmq_config[RMQ_CONFIG_SECTION]["vhost"],
-    }
-
-
-# Celery amqp settings
-BROKER_URL = get_rmq_broker()
-CELERY_RESULT_BACKEND = "amqp"  # Use RabbitMQ as the celery backend
-CELERY_RESULT_PERSISTENT = True  # Persist through a broker restart
-CELERY_TASK_RESULT_EXPIRES = 900  # Expire task results after 15 minutes
-CELERY_RESULT_EXCHANGE = "celeryresults"  # Default exchange - needed due to php-celery
-CELERY_QUEUES = (
-    Queue("podcast", exchange=Exchange("podcast"), routing_key="podcast"),
-    Queue(exchange=Exchange("celeryresults"), auto_delete=True),
-)
-CELERY_EVENT_QUEUE_EXPIRES = 900  # RabbitMQ x-expire after 15 minutes
-
-# Celery task settings
-CELERY_TASK_SERIALIZER = "json"
-CELERY_RESULT_SERIALIZER = "json"
-CELERY_ACCEPT_CONTENT = ["json"]
-CELERY_TIMEZONE = "Europe/Berlin"
-CELERY_ENABLE_UTC = True