Swagger conversion to OpenAPI3 with `allOf` makes `required` of the composed model get lost

[sebas2day]

Swagger-parser version: 2.1.2

Sample spec

swagger: "2.0"
info:
  title: composed model conversion test
  version: 1.0.0
paths:
  /composed:
    get:
      operationId: composed
      responses:
        "200":
          description: OK
          schema:
            $ref: "#/definitions/ComposedModel"
definitions:
  BaseModel:
    type: object
    required:
      - uuid
    properties:
      uuid:
        type: string
  ComposedModel:
    type: object
    required:
      - name
    allOf:
      - $ref: "#/definitions/BaseModel"
    properties:
      name:
        type: string

Description
Having a Swagger 2 specification that has a composed model (such as having an allOf) and converting that to OpenAPI 3 makes sure information is properly transformed into the new ComposedSchema, except for required. So the required properties information gets lost after conversion when it is being composed.

Expected result
I expected to keep required in there.

Actual result
No required to be found on ComposedModel.

Parsing result:

{
  "openapi": "3.0.1",
  "info": {
    "title": "composed model conversion test",
    "version": "1.0.0",
    "extensions": {}
  },
  "servers": [{ "url": "/" }],
  "paths": {
    "/composed": {
      "get": {
        "operationId": "composed",
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "*/*": {
                "schema": {
                  "$ref": "#/components/schemas/ComposedModel",
                  "extensions": {},
                  "exampleSetFlag": false
                },
                "exampleSetFlag": false
              }
            },
            "extensions": {}
          }
        },
        "extensions": {}
      },
      "extensions": {}
    }
  },
  "components": {
    "schemas": {
      "BaseModel": {
        "required": ["uuid"],
        "type": "object",
        "properties": {
          "uuid": {
            "type": "string",
            "extensions": {},
            "exampleSetFlag": false,
            "types": ["string"]
          }
        },
        "exampleSetFlag": false,
        "types": ["object"],
        "jsonSchema": {
          "type": "object",
          "required": ["uuid"],
          "properties": { "uuid": { "type": "string" } }
        }
      },
      "ComposedModel": {
        "properties": {
          "name": {
            "type": "string",
            "extensions": {},
            "exampleSetFlag": false,
            "types": ["string"]
          }
        },
        "extensions": {},
        "exampleSetFlag": false,
        "allOf": [
          { "$ref": "#/components/schemas/BaseModel", "exampleSetFlag": false }
        ]
      }
    }
  },
  "extensions": { "x-original-swagger-version": "2.0" }
}

using

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(Include.NON_NULL);
String json = mapper.writeValueAsString(openapi);