Send an email digest with suggested tasks based on skills

# Problem

We want to send an email that uses the (yet unfinished) task matcher to send an email digest with perhaps the top three most recommended, unassigned, open tasks for a user based on their skills.

We can attempt to send this once a week using Quantum jobs.

We'll likely need to be add in some sort of system for being able to unsubscribe from these emails so that future emails don't accidentally end up in spam.

Each task should list:

- skills (both matching and not matching)
- when the task was created

Ideally we would also factor in the task priority, but that might be a polish step.