Feature Request: Self-serve user deletion

[joethreepwood]

Feature request

Is your feature request related to a problem?

We're getting bigger and, as they say, you can't please everybody. Some users are going to want their accounts deleted and we're getting more requests for that. It's a pain having to deal with this one-by-one as users email in, both for us and them.

Users can already delete their orgs, their environments, etc. But they can't delete themselves.

Obviously we need some protections here to handle some edge case logic, such as:

• what if a user is an admin and they delete themselves, leaving no admins?
• what if a user is the only person in an org and they delete themselves, do we keep the org?
• what if a user is a member of multiple orgs?
• can we send this to other platforms we sync with, to fully remove their data?

Describe the solution you'd like

We should have a way users can delete themselves. Potentially with a time delay before it's fully processed.

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]