Malformed UTF-8 characters in PaginatedModelsLoader #2789

Describe the bug

#2540 added a json_encode call at https://github.com/nuwave/lighthouse/blob/master/src/Execution/ModelsLoader/PaginatedModelsLoader.php#L89 to compare models rather than toJson, which was changed to encoding the raw original values in #2550 to avoid some casted values not being able to json_encode. However, some raw values cannot be passed to json_encode either, like binary UUID representations as used by https://github.com/michaeldyrynda/laravel-model-uuid. The raw value is a string in PHP but it is not valid UTF-8, so json_encode fails with the JSON_ERROR_UTF8 error.

I am happy to assist with a PR here though I don't think this has an obvious solution so I wanted to discuss in an Issue before I went down that path.

Expected behavior/Solution

Comparison should complete without error while still comparing all values as needed.

• This could be worked around simply by passing the JSON_INVALID_UTF8_IGNORE or JSON_INVALID_UTF8_SUBSTITUTE flags to json_encode, but this likely has poor side effects I'm not currently thinking about by effectively hiding these values from the comparison.
• Ideally the comparison should correctly compare the full attributes as intended without failing on non-encodable values either pre- or post-cast.

Steps to reproduce

1. Define a has-many relationship between two models with a column using the Laravel Model UUID library (or similar non-UTF8 strings)
2. Return the relationship in a GraphQL field using the @hasMany(type: PAGINATOR) directive
3. Attempt to load the field, see the error during the json_encode call

Output/Logs

Safe\Exceptions\JsonException: Malformed UTF-8 characters, possibly incorrectly encoded in /.../vendor/thecodingmachine/safe/lib/Exceptions/JsonException.php:9
Stack trace:
#0 /.../vendor/thecodingmachine/safe/generated/8.1/json.php(20): Safe\Exceptions\JsonException::createFromPhpError()
#1 /.../vendor/nuwave/lighthouse/src/Execution/ModelsLoader/PaginatedModelsLoader.php(89): Safe\json_encode(Array)

Lighthouse Version

v6.70.1