The goal of this issue is to list all the changes that we aim to document in our Developer Changelog (/CHANGELOG.md). We need to move this knowledge to a guide in developer.piwik.org so that it's shared across team members, and clear to the developer community.

Context

Where we are today:

• We create the Piwik platform and offer developers a set of public APIs The Matomo platform, our public APIs, and maintaining backward compatibility #8125
• We maintain backward compatibility for those APIs.
• When changing or removing public APIs, we must first deprecate code following this process: Our work process when changing or removing a public API from the Matomo platform #8126
• We keep track of all platform changes relevant to developers in our Developer changelog

What to write in developer changelog

As a Piwik product team engineer, we keep the developer changelog up to date by noting any:

• change to a Reporting API method (eg. new API method added, deprecated, removed)
• change to Reporting API output (eg. a new field in an API response)
• change to Reporting API parameter (eg. parameter added, deprecated, removed)
• change to Tracking API parameter (eg. parameter added, deprecated, removed)
• change to Piwik JavaScript Tracker feature (eg. new feature, or removed feature)
• since PHP 8 argument names of public API's are also considered API
• new console command
• new parameter for a console command
• new developer guide
• update to a third party library
• any other relevant internal change that may interest developers

Developer changelog structure

These changes are organised in the developer changelog in the following categories:

• Breaking Changes
• Deprecations
• New features
• New APIs
• New commands
• New guides
• Library updates
• Internal change

(you will find the template at the bottom of CHANGELOG.md file)