A new Admin Panel for TYPO3

Summary

The goal of this initiative is to refactor the Admin Panel, add a new API, re-design it and add new functionality.

Background

The Admin Panel implementation was very old and had no API to extend the functionality (aside from a hook to add content). As programming paradigmns and possibilities changed quite a bit during the last twenty years, it's time to refactor the implementation and modernize the architecture. In v9 the refactored adminpanel was integrated, now the initiative focusses on developing further features - first in an extension, later maybe as part of the core.

Goals

Short-Term

Refactor current implementation and extract code from main AdminPanelView class
Have a dedicated system extension for the admin panel
Have a stable API for extending the admin panel

Mid-Term

The Admin Panel has been redesigned with the general backend CI in mind.

Long-Term

Database Query information is displayed in an Admin Panel Module
Log Messages can be shown via the Admin Panel
... tbd

Milestones

Extract AdminPanelView modules to one class per module with interface and API to register own modules #84045 [done]
Extract module specific code lines from general code (interface expansion might be necessary) [done]
Move AdminPanel to own system extension and let the modules be registered by the corresponding core extensions (f.e. fe_edit) [done]
Remove access to globals and use PSR-7 request object instead (introduce AdminPanel PSR-15 middleware) [interface expansion with $request might be necessary] [done]
Remove configuration via $_GET params (google the admin panel get vars and you'll see one of the reasons) [done as far as possible]
Render modules via fluid standalone [done]
Render outer panel via fluid standalone [done]
Re-Design the panel [done]
Introduce request cache to be able to build a standalone debugger tool [done]
Build a standalone debugger
Build an extension as incubator for new features [done]