[Mailer][Mime] Refactor S/MIME encryption handling in SMimeEncryptionListener

[alamirault]

Fix #20827

Having a SmimeCertificateRepositoryInterface implementation is a good thing I think.
I don't really how to introduce it.

[javiereguiluz]

I don't know much about this 🙏 but the previous example looked pretty convenient.

Is it really a bad practice? If it's not, maybe we can show both alternatives?

[alamirault]

I thinks it's ok, but I don't really know others possible implementations

[javiereguiluz]

Let's ask @Spomky. Could you please tell us if the example currently shown on Symfony Docs works and is valid? If it is, I think we should display both the current example and the new proposed ones (so folks don't overcomplicate things when not necessary). Thanks!

[Spomky]

Hi @alamirault and @javiereguiluz,

Yes, the example looks good.
The storage strategy is entirely up to the developers and in this example it is simply a folder-based approach.

The purpose of the SmimeCertificateRepositoryInterface is to resolve the certificate file path for a given email address, as the S/MIME encrypter expects a valid local file path to the certificate.

[Spomky]

The purpose of the method SmimeCertificateRepositoryInterface::findCertificatePathFor is to resolve the certificate file path for a given email address, as the S/MIME encrypter expects a valid local file path to the certificate.