Serialization of custom parameters nested in "parameters" field with Jackson and Kotlin

### Expected Behavior

```kotlin
throw Problem.builder()
.withType(URI.create("https://example.org/out-of-stock"))
.withTitle("Out of Stock")
.withStatus(HttpStatusType(HttpStatus.BAD_REQUEST))
.withDetail("Item B00027Y5QG is no longer available")
.with("product", "B00027Y5QG")
.build()
```

```json
{
"status": 400,
"title": "Out of Stock",
"detail": "Item B00027Y5QG is no longer available",
"type": "https://example.org/out-of-stock",
"parameters": {"product": "B00027Y5QG"}
}

```

### Actual Behaviour

```json
{
"localized_message": "Out of Stock: Item B00027Y5QG is no longer available",
"type": "https://example.org/out-of-stock",
"parameters": {
"product": "B00027Y5QG"
},
"detail": "Item B00027Y5QG is no longer available",
"status": 400,
"title": "Out of Stock"
}
```

### Steps To Reproduce

_No response_

### Environment Information

_No response_

### Example Application

_No response_

### Version

4.8.0

The issue names no source files, tests, or entry points. Start by reproducing the Kotlin/Jackson serialization described for version 4.8.0 and compare the actual and expected problem JSON. Done means the serialization behavior matches the expected structure without the reported discrepancy.

Written by the indexing model from the issue text.