[Bug]: Polymorphic types don't include composite schema reference

Description of the problem/issue

This project illustrates the problem. When having polymorphic types and using the swagger-gradle-plugin to generate the OpenAPI descriptor file, subtypes are missing the combined schema reference (allOf) to the parent type.

This is the current output in 2.2.41:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "properties" : { }
}

And this was the expected output in 2.2.40:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "allOf" : [ {
    "$ref" : "#/components/schemas/AttributeType"
  } ]
}

I debugged and the first pass of the model resolver for the parent type populates the reference correctly, however the model is redefined here and the reference is lost. I don't know enough of the model resolution to isolate a fix.

I suspect it might be a regression introduced while resolving https://github.com/swagger-api/swagger-core/issues/5003

Affected Version

2.2.41

Earliest version the bug appears in (if known):
2.2.41

Steps to Reproduce

Expand the project attached and execute:

./gradlew clean resolve

In order to compare the differences between 2.2.41 and 2.2.40, modify the gradle script to downgrade the dependency to swagger-core.

Expected Behavior

Subtypes should include a composite schema to the parent type like so

"DateAttributeTypeImpl" : {
  "type" : "object",
  "allOf" : [ {
    "$ref" : "#/components/schemas/AttributeType"
  } ]
}

Actual Behavior

Subtypes are created as independent models with no reference to the parent:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "properties" : { }
}

Logs / Stack Traces

none

Additional Context

Checklist

• I have searched the existing issues and this is not a duplicate.
• I have provided sufficient information for maintainers to reproduce the issue.

Start with ModelResolver.java around line 1133 and reproduce the regression using the attached project with ./gradlew clean resolve. Compare swagger-core 2.2.41 with 2.2.40 and trace where the parent reference is lost during model redefinition. Done means polymorphic subtypes such as DateAttributeTypeImpl again contain an allOf reference to AttributeType.