Big run number ranges cause timeout

[ptrstn]

If, for example, the lumisections are retrieved for a whole year, then the processing takes a long time and can lead to a timeout error.

To prevent this asynchronous task queues such as Celery + RabbitMQ should be used.

Links:

• https://stackoverflow.com/questions/45459738/django-long-request-timeout
• https://simpleisbetterthancomplex.com/tutorial/2017/08/20/how-to-use-celery-with-django.html
• http://docs.celeryproject.org/en/latest/getting-started/brokers/rabbitmq.html
• https://github.com/arteria/django-background-tasks