PageCache/AccessList: Add CIDR support

Author: tdgroot

app/code/Magento/PageCache/Model/System/Config/Backend/AccessList.php

@@ -24,7 +24,7 @@ public function beforeSave()
         parent::beforeSave();
 
         $value = $this->getValue();
-        if (!is_string($value) || !preg_match('/^[\w\s\.\-\,\:]+$/', $value)) {
+        if (!is_string($value) || !preg_match('/^[\w\s\.\-\,\:(\/\d+)?]+$/', $value)) {
             throw new LocalizedException(
                 new Phrase(
                     'Access List value "%1" is not valid. '

app/code/Magento/PageCache/Test/Unit/Model/System/Config/Backend/AccessListTest.php

@@ -52,6 +52,7 @@ public function getValidValues(): array
             [null, 'localhost'],
             ['127.0.0.1', '127.0.0.1'],
             ['127.0.0.1, localhost, ::2', '127.0.0.1, localhost, ::2'],
+            ['172.16.0.1/24, 2001:0db8:/32', '172.16.0.1/24, 2001:0db8:/32'],
         ];
     }