Add Nullable Utility Function to Support OpenAPI nullable Property

[casantosmu]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

Export a utility function Nullable that generates OpenAPI-compatible schemas with the nullable property.

Example:

const Nullable = <T extends TSchema>(schema: T) => Type.Unsafe<Static<T> | null>({ 
  ...schema, 
  nullable: true 
});

const T = Nullable(Type.String());  
// Output:
// {
//   type: 'string',
//   nullable: true
// }

I am happy to implement this feature if the proposal is approved.

Motivation

Improve developer experience.

Example

// ....
response: {
  201: Type.Object({
      name: Nullable(Type.String()),
  }),
}
// ....

Outputs:

      responses:
        "201":
          description: Default Response
          content:
            application/json:
              schema:
                type: object
                properties:
                  displayName:
                    type: string
                    nullable: true
                required:
                  - displayName