Important: #91070 - SMTP transport option 'transport_smtp_encrypt' changed to boolean 

See forge#91070

Description 

With https://forge.typo3.org/issues/90295 the allowed value for $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_encrypt'] has been changed to a boolean value.

symfony/mailer does no longer allow to specify the STARTTLS usage, as it will be used by default (if the server provides the needed support).

Therefore, the SMTP encryption configuration setting $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_encrypt'] is automatically updated by the install tool's silent configuration upgrade.

The configuration value (string)tls is removed to reflect that symfony/mailer expects (bool)false for STARTTLS. Other values like (string)ssl are converted too (bool)true.

No migration is needed at all, as no deprecation is thrown.