introduce sqlite foreign_key_constraints config option
introduce sqlite foreign_key_constraints config option

This enables the sqlite `foreign_key_constraints` option that was introduced with laravel/framework#26298 for all new installs.

The env variable DB_FOREIGN_KEYS was added to make it easier to handle this in testing (e.g. via phpunit.xml).

Gomasy/BooksManager,Gomasy/BooksManager,Gomasy/BooksManager