[BUG] sibling properties on reference objects

Description

Sibling properties such as readOnly and description are ignored when they are a sibling of a $ref property

openapi-generator version

5.3.0

OpenAPI declaration file content or url

{
    "description": "ACD routing status",
    "readOnly": true,
    "$ref": "#/definitions/RoutingStatus"
}

Generation Details

I see this happening across all languages I've used so far

Steps to reproduce

Generate any SDK with an open API file containing an object similar to the one above. Notice that the description and readOnly property will be ignored.

Related issues/PRs

It was fixed in this PR in the old version of swagger-core: https://github.com/swagger-api/swagger-core/pull/2502/files

Suggest a fix

I've spent a good few hours on this. Mostly trying to make changes in swagger-core to no success. I assume the issue is in swagger-core but I can't be 100% sure

Start by reproducing the issue with the JSON declaration shown, then trace how reference objects and sibling properties are handled in the OpenAPI parsing or schema-resolution path. Compare the behavior with the linked swagger-core PR; done means generated SDKs preserve sibling description and readOnly values instead of ignoring them.