feature #28842 [Validator] Deprecate checkMX and checkHost on Email validator (fabpot)

This PR was merged into the 4.2-dev branch.

Discussion
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[Validator] Deprecate checkMX and checkHost on Email validator

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | yes
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | fixes #27559 fixes #28665
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

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Commits
-------

c6009a0144 [Validator] deprecate checkMX and checkHost on Email validator

UPGRADE-4.2.md

@@ -261,6 +261,7 @@ TwigBundle
 Validator
 ---------
 
+ * The `checkMX` and `checkHost` properties of the Email constraint are deprecated
  * The component is now decoupled from `symfony/translation` and uses `Symfony\Contracts\Translation\TranslatorInterface` instead
  * The `ValidatorBuilderInterface` has been deprecated and `ValidatorBuilder` made final
  * Deprecated validating instances of `\DateTimeInterface` in `DateTimeValidator`, `DateValidator` and `TimeValidator`. Use `Type` instead or remove the constraint if the underlying model is type hinted to `\DateTimeInterface` already.

UPGRADE-5.0.md

@@ -238,6 +238,7 @@ TwigBundle
 Validator
 --------
 
+ * The `checkMX` and `checkHost` properties of the Email constraint were removed
  * The `Email::__construct()` 'strict' property has been removed. Use 'mode'=>"strict" instead.
  * Calling `EmailValidator::__construct()` method with a boolean parameter has been removed, use `EmailValidator("strict")` instead.
  * Removed the `checkDNS` and `dnsMessage` options from the `Url` constraint.

src/Symfony/Component/Validator/Constraints/Email.php

@@ -28,7 +28,15 @@ class Email extends Constraint
     public const VALIDATION_MODE_LOOSE = 'loose';
 
     const INVALID_FORMAT_ERROR = 'bd79c0ab-ddba-46cc-a703-a7a4b08de310';
+
+    /**
+     * @deprecated since Symfony 4.2.
+     */
     const MX_CHECK_FAILED_ERROR = 'bf447c1c-0266-4e10-9c6c-573df282e413';
+
+    /**
+     * @deprecated since Symfony 4.2.
+     */
     const HOST_CHECK_FAILED_ERROR = '7da53a8b-56f3-4288-bb3e-ee9ede4ef9a1';
 
     protected static $errorNames = array(
@@ -49,11 +57,19 @@ class Email extends Constraint
     );
 
     public $message = 'This value is not a valid email address.';
+
+    /**
+     * @deprecated since Symfony 4.2.
+     */
     public $checkMX = false;
+
+    /**
+     * @deprecated since Symfony 4.2.
+     */
     public $checkHost = false;
 
     /**
-     * @deprecated since Symfony 4.1. Set mode to "strict" instead.
+     * @deprecated since Symfony 4.1, set mode to "strict" instead.
      */
     public $strict;
     public $mode;
@@ -64,6 +80,14 @@ class Email extends Constraint
             @trigger_error(sprintf('The "strict" property is deprecated since Symfony 4.1. Use "mode"=>"%s" instead.', self::VALIDATION_MODE_STRICT), E_USER_DEPRECATED);
         }
 
+        if (\is_array($options) && array_key_exists('checkMX', $options)) {
+            @trigger_error('The "checkMX" property is deprecated since Symfony 4.2.', E_USER_DEPRECATED);
+        }
+
+        if (\is_array($options) && array_key_exists('checkHost', $options)) {
+            @trigger_error('The "checkHost" property is deprecated since Symfony 4.2.', E_USER_DEPRECATED);
+        }
+
         if (\is_array($options) && array_key_exists('mode', $options) && !\in_array($options['mode'], self::$validationModes, true)) {
             throw new \InvalidArgumentException('The "mode" parameter value is not valid.');
         }

src/Symfony/Component/Validator/Tests/Constraints/EmailValidatorTest.php

@@ -317,6 +317,7 @@ class EmailValidatorTest extends ConstraintValidatorTestCase
     /**
      * @dataProvider getDnsChecks
      * @requires function Symfony\Bridge\PhpUnit\DnsMock::withMockedHosts
+     * @group legacy
      */
     public function testDnsChecks($type, $violation)
     {
@@ -353,6 +354,7 @@ class EmailValidatorTest extends ConstraintValidatorTestCase
 
     /**
      * @requires function Symfony\Bridge\PhpUnit\DnsMock::withMockedHosts
+     * @group legacy
      */
     public function testHostnameIsProperlyParsed()
     {
@@ -368,6 +370,7 @@ class EmailValidatorTest extends ConstraintValidatorTestCase
 
     /**
      * @dataProvider provideCheckTypes
+     * @group legacy
      */
     public function testEmptyHostIsNotValid($checkType, $violation)
     {