Breaking: #96291 - Disallow DB connection before TCA is loaded

See forge#96291

Description

Accessing the database API before TCA is loaded is considered to be a logic mistake, as TCA is required to generate the expected database schema.

Impact

Extensions that access the TYPO3 database API in ext_localconf.php files or TCA files will not work any more, because TYPO3 will throw an exception in this case.

Affected Installations

TYPO3 installations with third-party extensions, that access database API before TCA is loaded.

Migration

Database API can be accessed earliest in the \TYPO3\CMS\Core\Core\Event\BootCompletedEvent .