[ASPNETCORE] Nullable custom valuetypes

Currently I have a custom type declared as such:

"typeMappings": {
    "string+my-custom-value-type": "MyCustomValueType"
}

MyCustomValueType is a struct (e.g. value type).

In non-nullable context the type is generated as expected:

"exampleProperty": {
  "type": "string",
  "format": "my-custom-value-type"
}

public MyCustomValueType ExampleProperty { get; set; }

But whenever I define a property as nullable the generated property is missing the explicit ? (nullable) suffix required for value types.

OpenAPI spec:

"exampleProperty": {
  "type": "string",
  "format": "my-custom-value-type",
  "nullable": true
}

public MyCustomValueType ExampleProperty { get; set; }

Expected:

public MyCustomValueType? ExampleProperty { get; set; }

Is there a way to tell the (aspnetcore) generator to treat a custom type as a value type?

Start by reproducing the ASP.NET Core generation with the supplied typeMappings and OpenAPI schema, then inspect the generator's handling of nullable custom types. The issue names no source files or tests, so locate the type-mapping and nullable-property generation entry points. Done means a nullable custom struct is emitted with the explicit ? suffix while the non-nullable case remains unchanged.