[12.x] Fix Validator::appendRules() with pipe-separated rule strings

[leo108]

Summary

Fixes a bug where Validator::appendRules() throws exception when new rules use pipe-separated strings (e.g., 'required|string|min:5'). The issue occurs because array_merge_recursive() merges already-parsed arrays with unparsed strings.

Step to reproduce

When using appendRules() with pipe-separated rules:

$validator = new Validator($trans, ['name' => 'ab'], ['name' => 'required']);
$validator->appendRules(['name' => 'string|min:5']);
$validator->fails(); // Throws: Method validateString|min does not exist

Solution

Modified Validator::appendRules() to pre-process the new rules by exploding pipe-separated strings into arrays before calling array_merge_recursive().