feat(periodic-digest): add periodic digest notification setting

[raquelmsmith]

Problem

People need to be able to turn these digests off completely and for specific projects.

Changes

• Added the notification settings to the user.
• Made a util function to check the user notif settings
  • I don't love how this has to have specific code written for every setting type, but because they could either be true-default or false-default settings (ie does setting the value to true disable or enable it? we could have a mix) this is how we can handle it I guess? Also lets us handle setting overrides, like the global "disable all digests" setting that should override any per-project setting.
• Added to the user settings page
  

I don't love this UI, open to other good ideas.

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Does this work well for both Cloud and self-hosted?

N/A

How did you test this code?

All tests still pass, importantly the usage_report ones because I changed the capture_event function location. So hopefully that means this didn't break anything.

[posthog-bot]

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