Suggestion: Make MAILER_URL syntax in .env consistent with Doctrine

[ThomasLandauer]

This is a follow up of symfony/symfony#30316

I'm suggesting to change the syntax of MAILER_URL for smtp:// in .env from

MAILER_URL=smtp://localhost:25?encryption=ssl&username=&password=

to

MAILER_URL=smtp://username:password@localhost:25?encryption=ssl

Arguments:

1. The syntax username:password@host has been around for some time and is even mentioned in the RFC (albeit partly deprecated): https://tools.ietf.org/html/rfc3986#section-3.2.1

2. Doctrine uses it too: https://symfony.com/doc/current/doctrine.html#configuring-the-database

3. It's already in use for gmail://: https://symfony.com/doc/current/email.html#using-gmail-to-send-emails

[ThomasLandauer]

Just noticing that this is already possible for the url configuration parameter: https://symfony.com/doc/current/reference/configuration/swiftmailer.html#url

So is what I'm asking for already implemented in the code and just needs to be documented at https://symfony.com/doc/current/email.html#configuration and in .env.dist?

[eeemarv]

#234 duplicate (PR #263)