Document serialization behavior when passing object to ErrorBuilder.SetExtension

[shravan2x]

Product

Hot Chocolate

Is your feature request related to a problem?

When adding a custom extension to an error, it's serialized by default using a format I don't recognize. But when a JsonElement is used instead, it's reliably serialized using JSON.

Case 1:

IError err = ErrorBuilder.New()
    .SetCode("TEST")
    .SetMessage("Test message.")
    .SetExtension("testExtension", new { prop = "val" })
    .Build();

// "extensions": {
//   "code": "TEST",
//   "testExtension": "{ prop = val }"
// }

Case 2:

IError err = ErrorBuilder.New()
    .SetCode("TEST")
    .SetMessage("Test message.")
    .SetExtension("testExtension", JsonSerializer.SerializeToElement(new { prop = "val" }))
    .Build();

// "extensions": {
//   "code": "TEST",
//   "testExtension": {
//     "prop": "val"
//   }
// }

The solution you'd like

Could this behavior be documented at https://chillicream.com/docs/hotchocolate/v14/api-reference/error-filter?