Can I Specify a Flexible Properties of Any Type on a Schema? #2773

Hi OpenAPI-Specification team,
We are on OpenAPI Specification 3.0.1. We have a highly customizable platform that allows users to create custom fields on a schema. For example, let's say we provide a schema called "Order" out of the box:

Order:
      type: object
      properties:
        id:
          type: integer
          format: int64
        shipDate:
          type: string
          format: date-time
        status:
          type: string
          description: Order Status
          enum:
          - placed
          - approved
          - delivered
        complete:
          type: boolean
          default: false
      xml:
        name: Order

Let's say the customer retrieve an OpenAPI specification (OAS) that contains the above schema. They generate a client library using the OAS and can use it in code to populate the field value like following:

order.setShipDate("10/29/2021");

Now let's say they add a new custom field call "quantity" to the order schema:

quantity:
  type: integer
  format: int32

But they don't regenerate client library using the updated OAS. , so they can't do order.setQuantity(2); in their code.

If possible, we would like to reduce the number of times that customers need to regenerate OAS and client library. We are thinking about defining a flexible field on the schema that can support any number of properties of any type. For example, something like

properties:
  anyPropertyName:
     type: anyType

And by doing so, we hope to enable following capability in client code:

order.setShipDate("10/29/2021");  // "ShipDate" is a property provided out of the box, so customers can directly do setShipDate
order.setField("quantity", 2);  // "quantity" is a customer-defined field, not a property provided out of the box, so customers need to use setField(fieldName, fieldValue) to populate the object
order.setField("shippingCity", "San Francisco");  // "shippingCity" is a customer-defined field, not a property provided out of the box, so customers need to use setField(fieldName, fieldValue) to populate the object

So, my question: Is there anything in OpenAPI specification 3.0.1 that allow us to specify a flexible property under schema that allow us to do object.setField(fieldName, fieldValue) ?

Thanks!