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

See Issue #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 BootCompleted event.