[BUG] Unable to generate shared external reference DTOs for open API 3.1

Description

I try to move from openapi 3.0.3 to 3.1, but I have a strange behaviour with ref schema.
With 3.0.3 ref schemas are generated (java/spring) with a dedicated Dto, example a schema common.Amount creates a Dto CommonAmount that use as is from all the places.
With 3.1 it now creates a new schema for all the places it’s used.
It’s not related to the generator, but to the parsing: It changed in file OpenAPIV3Parser, L211 if (result.getOpenAPI().getOpenapi() != null && result.getOpenAPI().getOpenapi().startsWith("3.1")) {

I had a maven/springboot project to reproduce it: https://github.com/pkernevez/pb-openapi
The only difference in swaggers “3.0” and “3.1" are the version in the first line.
In my example, I have a share type : common.Amount (a quantity and a currency).
With 3.0.3 I have a shared type CommonAmount, with 3.1 I now have a new type for each usage (here market value).
Why this behaviour changed ?
Is there a way to restore the previous way ?

Having a new class for each usage is an issue to define only once shared code, like mapping Entity <-> Dto

openapi-generator version

Tested with :

• 7.4.0
• 7.5.0-SNAPSHOT on April 11th.

OpenAPI declaration file content or url

• v3.0.3 version
  https://github.com/pkernevez/pb-openapi/blob/master/src/main/resources/swagger/accounting-swagger-v3-0.yaml
• v3.1.0 version:
  https://github.com/pkernevez/pb-openapi/blob/master/src/main/resources/swagger/accounting-swagger-v3-1.yaml

Generation Details

APIs are the same, the issues is for Dtos.

Steps to reproduce

mvn clean install
find target/generated-sources/src/main/java/net/kernevez/generated

Reproduce the difference with the linked pb-openapi Maven project and compare the generated DTOs for its OpenAPI 3.0.3 and 3.1 files. Then inspect OpenAPIV3Parser around line 211, where the 3.1 path is selected. Done means determining why shared external references produce per-use schemas and restoring shared DTO generation without changing the intended 3.1 parsing behavior.