Add long running function decorator

Description

This task is to create a new decorator in ucam-faas that supports long-running functions. This decorator should live in a separate sub-module.

Further details

The long running function decorator should ensure that instead of starting a flask container that responds to HTTP requests, when the container is started the python code decorated (i.e. the handler code) is executed.

We will also need a base docker container for long running jobs to be created and published for downstream implementers to use.

Task list

Acceptance criteria

• Decorator exists for long running jobs
• Long running job containers exit 0 on success, or non-zero on failure
• Base docker container for long running jobs exists
  • Example long-running job provided

Links/references