Make call to processing backend async

[jonodrew]

As a user
I want to know my request is being processed
So that I can stop worrying and get on with my day

[jonodrew]

So there are a couple of approaches here. Thinking out loud, we could:

• use Celery and Redis for asynchronous processing. This introduces more complexity, but not much. Redis instances are cheap - there's a free tier on Heroku - but running it locally probably means using something like docker-compose
• alternatively, the request could be sent and the user emailed a copy of the completed matchings. However, this routes the data through more points and, given that the data is deleted as quickly as possible, means that it may never get through.

[jonodrew]

On reflection, I'm going to do docker-compose for local dev and use a hosted redis server in production