Support for `z.lazy()` and recursive schemas

[rattrayalex]

Currently, this code (copied from zod's recursive types docs):

const baseCategorySchema = z.object({
  name: z.string(),
});

type Category = z.infer<typeof baseCategorySchema> & {
  subcategories: Category[];
};

const categorySchema: z.ZodType<Category> = baseCategorySchema.extend({
  subcategories: z.lazy(() => categorySchema.array()),
});

const registry = new OpenAPIRegistry();
registry.register("Category", categorySchema);

const generator = new OpenAPIGenerator(registry.definitions, "3.0.0");

try {
  const document = generator.generateDocument({
    info: {
      version: "1.0.0",
      title: "My API",
    },
    servers: [{ url: "v1" }],
  });
  console.log(document);
} catch (err) {
  console.error(err);
}

Throws this error:

UnknownZodTypeError {
  message: 'Unknown zod object type, please specify `type` and other OpenAPI props using `ZodSchema.openapi`.',
  data: {
    currentSchema: { getter: [Function (anonymous)], typeName: 'ZodLazy' },
    schemaName: undefined
  }
}

Ideally, it would generate an OpenAPI spec like this:

const document = {
  components: {
    schemas: {
      Category: {
        type: "object",
        properties: {
          name: { type: "string" },
          subcategories: {
            type: "array",
            items: { $ref: "#/components/schemas/Category" },
          },
        },
      },
    },
  },
  ...etc,
};

This may require automatic resolution of registered schemas to $refs, which I filed here: #142

[AGalabov]

@rattrayalex thank you for this. Lazy schemas are something that we do not support at all as of today. I'll take a look at it.