[symfony/mailgun-mailer] Align env examples with README

[ttskch]

Q	A
License	MIT
Doc issue/PR	N/A

The existing examples only show the bare mailgun:// scheme (which resolves to MailgunHttpTransport) and mailgun+smtp://. The mailgun+api:// scheme is missing, and mailgun:// is easily misinterpreted as "the default/API transport" while it actually uses the raw MIME endpoint that lacks first-class support for features like recipient-variables.

This aligns the recipe with the three explicit schemes documented in the current mailgun-mailer README:

• mailgun+smtp:// (SMTP)
• mailgun+https:// (HTTP, raw MIME)
• mailgun+api:// (API)

Making each transport explicit helps users pick the right one for their use case.

[github-actions]

Thanks for the PR 😍

How to test these changes in your application

1. Define the SYMFONY_ENDPOINT environment variable:

   # On Unix-like (BSD, Linux and macOS)
   export SYMFONY_ENDPOINT=https://raw.githubusercontent.com/symfony/recipes/flex/pull-1533/index.json
   # On Windows
   SET SYMFONY_ENDPOINT=https://raw.githubusercontent.com/symfony/recipes/flex/pull-1533/index.json

2. Install the package(s) related to this recipe:

   composer req symfony/flex
   composer req 'symfony/mailgun-mailer:^4.4'

3. Don't forget to unset the SYMFONY_ENDPOINT environment variable when done:

   # On Unix-like (BSD, Linux and macOS)
   unset SYMFONY_ENDPOINT
   # On Windows
   SET SYMFONY_ENDPOINT=

Diff between recipe versions

In order to help with the review stage, I'm in charge of computing the diff between the various versions of patched recipes.
I'm going keep this comment up to date with any updates of the attached patch.

symfony/mailgun-mailer

4.3 vs 4.4

diff --git a/symfony/mailgun-mailer/4.3/manifest.json b/symfony/mailgun-mailer/4.4/manifest.json
index 576fd92f..80a6c62e 100644
--- a/symfony/mailgun-mailer/4.3/manifest.json
+++ b/symfony/mailgun-mailer/4.4/manifest.json
@@ -1,10 +1,7 @@
 {
     "env": {
-        "#1": "MAILGUN_USERNAME=",
-        "#2": "MAILGUN_PASSWORD=",
-        "#3": "MAILER_DSN=smtp://$MAILGUN_USERNAME:$MAILGUN_PASSWORD@mailgun",
-        "#4": "MAILGUN_KEY=",
-        "#5": "MAILGUN_DOMAIN=",
-        "#6": "MAILER_DSN=http://$MAILGUN_KEY:$MAILGUN_DOMAIN@mailgun"
+        "#1": "MAILER_DSN=mailgun+smtp://USERNAME:PASSWORD@default?region=us",
+        "#2": "MAILER_DSN=mailgun+https://KEY:DOMAIN@default?region=us",
+        "#3": "MAILER_DSN=mailgun+api://KEY:DOMAIN@default?region=us"
     }
 }