Implement posthog_events submodule to track user actions

Let's keep it at "posthog_php_events" for now. We could also rename it to "posthog_events", to also have access to the js.

I am not really seeing the benefit of creating custom events for all of these user hooks. Why do we care if a user is blocked, unblocked, has updated their credentials, has deleted their account etc.?

Currently, the user is identified on login server / client sided, and that's most important. I understand the use of custom events for specific sites (e.g. how many people bought product a, how many bought product b), but not here? Let's discuss this first, before implementing.

We care, because these are important events or conversions for analytics. If you want a report on how many users were blocked in month X or how many accounts were deleted, you need this information.

What do you mean by

updated their credentials

? I can't see that requiremen above.
But the events you listed are all of minor importance, while the issue summary lists the most important events.

Let's keep it at "posthog_php_events" for now. We could also rename it to "posthog_events", to also have access to the js.

Definitely yes, tracking JS events is not a Drupal think and it's easy to be done. We're providing a DRUPAL specific submodule here, which adds events for typical DRUPAL events, that's the point. We're not creating an events SDK. Maybe that was unclear.

A super important one is confirming the email address (= registration) ( ✨ Add server-side tracking for registration confirmation Active ) which means showing the page after clicking the password confirmation link. That's the only place where you can be sure that this conversion (registration) was really finished.

All the other events beside these 4 above are quick-wins which already have Drupal hooks and should be easily implemented in 3 lines, that's why I think it makes sense. We can copy them from the billwerk module.

PS: Of course many events will also be available in the ECA integration as alternative, but this is more lightweight.

What do you mean by

updated their credentials

Probably "hook_user_update()". But yea, I still feel a LOT of these hooks have minor importance, but yea it's basic boilerplate code, so why not.

Okay, yes I think "profile updated" is very very minor, as the consequences are unclear. But many of the other events have business meaning.

Alright, done, please review!