Allow to use symfony/mailer and make the mailer service optionnal

[tristanbes]

Following this PR I cherry picked the commit making the mailer service optional and then I made possible to work with symfony/mailer

Right now, If you only have symfony/mailer on your >=4.3 project, you can't use FOSUserBundle because

Argument 1 passed to FOS\UserBundle\Mailer\TwigSwiftMailer::__construct() must be an instance of Swift_Mailer, instance of Symfony\Component\Mailer\Mailer given

Also, having both symfony/mailer and symfony/swiftmailer-bundle is not possible.

EDIT: In Symfony 4.3.1, they renamed the service id from mailer to mailer.mailer for the MailerInterface

[rufinus]

This seems dangerous - yes you cant have swiftmailer-bundle AND symonfy/mailer - but you can have symfony/mailer AND swiftmailer (without the bundle.)

[louia]

FOSUserBundle always not working ?

[comur]

Hi,

I have the exact same problem. Did someone find a workaround ?

Thx

[stof]

Closing this PR, as it is not the proper way of adding support for symfony/mailer, and the checks for mailers compatible with the configured fos_user.mailer service should not be removed.

[mpdude]

So #3042 is a … solution?