Describe the bug
I am using an ObjectId with the @ParameterObject, this prevent the doc from being generated and fail with a StackOverflowError. This is the error I got when I applied your suggestions (my User object actually had an ObjectId property).

To Reproduce
Use this HelloController (Kotlin):

@RestController
@RequestMapping("/hello")
class HelloController {

    @GetMapping
    fun hello(@ParameterObject id: ObjectId) {
    }

    @Bean
    fun openApi(): OpenAPI {
        return OpenAPI()
            .schema("ObjectId", Schema<ObjectId>().type("string"))
    }
}

(The schema is not needed to reproduce the issue, but it shows what I was expecting to see)

Expected behavior
Doc is displayed correctly with id as string

Screenshots