[Language Agnostic] Regression between versions 2.3.1 and 2.4.5 finding some response type definitions

Description

I can't tell which version specifically caused this regression because my project doesn't build on any versions in between 2.3.1 and 2.4.5.

Here is the spec where this occurs:

{
  "info": {
  },
  "paths": {
    "/user/email/v1": {
      "post": {
        "description": "email address",
        "operationId": "post_user_email_v1",
        "parameters": [
          {
            "description": "The future business user's email address. AdditionalProperties are allowed in order to accept utm_params",
            "in": "body",
            "name": "body",
            "required": true,
            "schema": {
              "additionalProperties": true,
              "properties": {
                "enc_email_addr": {
                  "description": "An email address",
                  "type": "string"
                },
                "utm_campaign": {
                  "description": "(Optional) The campaign of the request, provided by the deep link URL",
                  "type": "string"
                }
              },
              "required": [
                "enc_email_addr"
              ],
              "type": "object",
              "x-model": "PostUserEmailV1_RequestData"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "A successful request will return a email address",
            "examples": {
              "application/json": {
                "email": "testuser@example.com"
              }
            },
            "schema": {
              "additionalProperties": false,
              "properties": {
                "email": {
                  "description": "Email address",
                  "type": "string"
                }
              },
              "required": [
                "email"
              ],
              "type": "object",
              "x-model": "PostUserEmailV1_ResponseData"
            }
          },
          "default": {
            "description": "Error response",
            "schema": {
              "$ref": "#/definitions/ErrorResponse"
            }
          }
        }
      }
    }
  },
  "produces": [
    "application/json"
  ],
  "schemes": [
    "http"
  ],
  "swagger": "2.0"
}

With the above example, the following are the contents of allDefinitions in fromModel(name: String, model: Model, allDefinitions: MutableMap<String, Model>?): CodegenModel
2.3.1:
The request parameters model
The response parameters model
2.4.5:
The request parameters model

Removing "additionalProperties": false, from the response schema "solves" the problem. This of course isn't a real solution, but it gets the response model included in allDefinitions.

Swagger-codegen version

2.3.1 is the last working version. This bug still exists in 3.0.14. It was introduced some time between 2.3.1 and 2.4.5. It is a regression as far as I can tell.

Swagger declaration file content or url

See json above

Command line used for generation

We're using custom tooling on top of swagger-codegen. I can try and figure out what command ends up getting used if it would be helpful though.

Steps to reproduce

See above

Related issues/PRs

Similar issue from May. My issue adds the additional information that this behavior is a regression and which versions it may have been introduced in.
https://github.com/swagger-api/swagger-codegen/issues/9262

Suggest a fix/enhancement

See linked issue.

Start at fromModel(name: String, model: Model, allDefinitions: MutableMap<String, Model>?) and reproduce the regression with the supplied Swagger 2.0 specification across versions 2.3.1, 2.4.5, and 3.0.14. Done means the response model is included in allDefinitions without removing additionalProperties: false.