Implement better email validation support

These changes allow for multiple email validators to be added when checking for valid emails. This is a continuation of the previous PR: laravel/framework#26503

Basically this allows for two things:

- Make use of multiple email validators provided by the egulias/email-validator package
- Use the previous (and much requested) filter_var validation

By default nothing's breaking because it'll still use the RFC validator to when no validators are passed to the email validation rule. But you can opt to include different ones or multiple ones:

    'email' => 'email:rfc,dns'

Or opt for the pre-5.8 behavior:

    'email' => 'email:filter'

Which will use `filter_var` to validate the email address. This should give people a little more flexibility when doing email validation.

Concerns/FilterEmailValidation.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace Illuminate\Validation\Concerns;
+
+use Egulias\EmailValidator\EmailLexer;
+use Egulias\EmailValidator\Exception\InvalidEmail;
+use Egulias\EmailValidator\Validation\EmailValidation;
+use Egulias\EmailValidator\Warning\Warning;
+
+class FilterEmailValidation implements EmailValidation
+{
+    /**
+     * Returns true if the given email is valid.
+     *
+     * @param string $email The email you want to validate.
+     * @param EmailLexer $emailLexer The email lexer.
+     *
+     * @return bool
+     */
+    public function isValid($email, EmailLexer $emailLexer)
+    {
+        return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
+    }
+
+    /**
+     * Returns the validation error.
+     *
+     * @return InvalidEmail|null
+     */
+    public function getError()
+    {
+        return null;
+    }
+
+    /**
+     * Returns the validation warnings.
+     *
+     * @return Warning[]
+     */
+    public function getWarnings()
+    {
+        return [];
+    }
+}

Concerns/ValidatesAttributes.php

@@ -20,6 +20,10 @@
 use Symfony\Component\HttpFoundation\File\File;
 use Egulias\EmailValidator\Validation\RFCValidation;
 use Symfony\Component\HttpFoundation\File\UploadedFile;
+use Egulias\EmailValidator\Validation\DNSCheckValidation;
+use Egulias\EmailValidator\Validation\SpoofCheckValidation;
+use Egulias\EmailValidator\Validation\NoRFCWarningsValidation;
+use Egulias\EmailValidator\Validation\MultipleValidationWithAnd;
 
 trait ValidatesAttributes
 {
@@ -621,16 +625,35 @@ protected function extractDistinctValues($attribute)
      * Validate that an attribute is a valid e-mail address.
      *
      * @param  string  $attribute
-     * @param  mixed   $value
+     * @param  mixed  $value
+     * @param  array  $parameters
      * @return bool
      */
-    public function validateEmail($attribute, $value)
+    public function validateEmail($attribute, $value, $parameters)
     {
         if (! is_string($value) && ! (is_object($value) && method_exists($value, '__toString'))) {
             return false;
         }
 
-        return (new EmailValidator)->isValid($value, new RFCValidation);
+        $validations = collect($parameters)
+            ->unique()
+            ->map(function ($validation) {
+                if ($validation === 'rfc') {
+                    return new RFCValidation();
+                } elseif ($validation === 'strict') {
+                    return new NoRFCWarningsValidation();
+                } elseif ($validation === 'dns') {
+                    return new DNSCheckValidation();
+                } elseif ($validation === 'spoof') {
+                    return new SpoofCheckValidation();
+                } elseif ($validation === 'filter') {
+                    return new FilterEmailValidation();
+                }
+            })
+            ->values()
+            ->all() ?: [new RFCValidation()];
+
+        return (new EmailValidator)->isValid($value, new MultipleValidationWithAnd($validations));
     }
 
     /**