UPGRADE

v5.x > v6.x

Changed compatibility so PHP 8

v4.x > v5.x

Changed compatibility so Symfony 6

v3.x > v4.x

Changed localizeddate to format_datetime

v2.x > v3.x

c975LEmailBundle now use Symfony\Component\Mailer\MailerInterfaceand Symfony\Component\Mime\Email which are NOT compatible with Symfony 3.x.

v1.x > v2.x

When upgrading from v1.x to v2.x you should(must) do the following if they apply to your case:

The parameters entered in config.yml are not used anymore as they are managed by c975L/ConfigBundle, so you can delete them.
As the parameters are not in config.yml, we can't access them via $this[->container]->getParameter(), so you have to replace $this->getParameter('c975_l_contactform.XXX') by $configService->getParameter('c975LContactForm.XXX'), where $configService is the injection of c975L\ConfigBundle\Service\ConfigServiceInterface.
Before the first use of parameters, you MUST use the console command php bin/console config:create to create the config files with default data.