changes.md

## 9.4.0

#### Project

#### OAP Server

* Add `ServerStatusService` in the core module to provide a new way to expose booting status to other modules.
* Adds Micrometer as a new component.(ID=141)
* Refactor session cache in MetricsPersistentWorker.

#### UI

#### Documentation

All issues and pull requests are [here](https://github.com/apache/skywalking/milestone/160?closed=1)