Breaking: #85398 - Drop documentation extension

Description

Fetching and rendering extension and core manuals directly within the backend using the documentation extension has been dropped from the TYPO3 backend.

The module never found broad acceptance and usage in the community, had various hard to resolve flaws and has been a maintenance burden for the documentation team ever since.

Impact

The Documentation module does not exist anymore and cannot be used to display manuals in the TYPO3 backend.

The previously required extension "documentation" is not available anymore.

New installations do not have the documentation extension installed by default.

Affected Installations

Every TYPO3 instance.

Migration

Current documentation of core functionality, core extensions and community extensions can always be found on docs directly.

Flush all TYPO3 Core Caches to ensure that PackageStates.php is rebuilt without the documentation extension.

For composer installations, ensure that the dependency to typo3/cms-documentation is removed.

Extensions authors need to ensure that dependencies to EXT:documentation are removed, if they existed before.