Context:

For now, we want to add a cronTrigger which defaults to Monday at 9AM to send digest emails instead of allowing users to customise the digest interval. 

This should also be documented in the user guide and config docs.

AT:

• digest emails are sent using cron trigger that defaults to Monday 9am
• checkInterval field is removed from digests
• confluence API docs are adjusted
• user guide and config docs are updated ==> do with follow up after Fe is adjusted for screenshots
• FE follow up to adjust UI