[FEATURE] Enable SQL connection initialization
Some database setups might need to run some initial SQL statement after
a connection has been established. Examples are date/time format options
for Oracle or charset settings for MySQL.
For MySQL UTF-8 support was potentially broken, depending on the system
setup. This can be fixed by using the new initialization option:
FLOW3: persistence: doctrine: dbal:
sessionInitialization: 'SET NAMES utf8 COLLATE utf8_unicode_ci'