Required nullable objects are not allowed to be null

[bruno-f-cruz]

Consider the following schema where both inner_optional and inner_required are nullable:

{
  "definitions": {
    "Object": {
      "properties": {
        "foo": {
          "title": "Foo",
          "type": "string"
        },
        "bar": {
          "title": "Bar",
          "type": "integer"
        }
      },
      "required": [
        "foo",
        "bar"
      ],
      "title": "Object",
      "type": "object"
    }
  },
  "properties": {
    "inner_optional": {
      "default": null,
      "oneOf": [
        {
          "$ref": "#/definitions/Object"
        },
        {
          "type": "null"
        }
      ]
    },
    "inner_required": {
      "oneOf": [
        {
          "$ref": "#/definitions/Object"
        },
        {
          "type": "null"
        }
      ]
    }
  },
  "required": [
    "inner_required"
  ],
  "title": "Container",
  "type": "object"
}

Deserialization using json fails if the "inner_required" is set to null but not the optional one, despite both evaluating to null. I am not sure this is a problem with sgen itself. Looking at the c# class definitions the only obvious difference is the Newtonsoft attribute Required. After some experimentation, I believe that the generator should use Newtonsoft.Json.Required.AllowNull instead of Newtonsoft.Json.Required.Always for these situations (ie.. when prop is nullable). See documentation here (https://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_Required.htm)
Find some useful examples attached include schema, csharp code, bonsai workflow and test json instances that reproduce the problem.
test_deser.zip