Change implementation to ensure one of current use cases is not broken. Add case with slash in regression integration test.

Author: wojtekn

app/code/Magento/Search/Model/SynonymAnalyzer.php

@@ -137,8 +137,10 @@ private function getSearchPattern(array $words): string
     {
         $patterns = [];
         for ($lastItem = count($words); $lastItem > 0; $lastItem--) {
+            $words = array_map(function ($word) {
+               return preg_quote($word, '/');
+            }, $words);
             $phrase = implode("\s+", \array_slice($words, 0, $lastItem));
-            $phrase = preg_quote($phrase, '/');
             $patterns[] = '^' . $phrase . ',';
             $patterns[] = ',' . $phrase . ',';
             $patterns[] = ',' . $phrase . '$';

dev/tests/integration/testsuite/Magento/Search/Model/SynonymAnalyzerTest.php

@@ -78,6 +78,10 @@ public static function loadGetSynonymsForPhraseDataProvider()
                 'phrase' => 'schlicht',
                 'expectedResult' => [['schlicht', 'natürlich']]
             ],
+            'withSlashInSearchPhrase' => [
+                'phrase' => 'orange hill/peak',
+                'expectedResult' => [['orange', 'magento'], ['hill/peak']]
+            ],
         ];
     }