5 years of UnifiedPush

It has already been 5 years since UnifiedPush started! It also means I don't have any Play Services, the official or microG reimplementation, for 5 years now. It is a good moment to do a recap, and think about what can be UnifiedPush in 5 years. It turns out I don't remember in details how all started, I need to read some historical pull requests and chats. Why do I need push notifications? I…