[BUG] [ASPNETCORE] Dictionary parameter now generated as object

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Originally the additionalProperties: true would generate a Dictionary parameter for the method signature. Since v7.16.0 it now just generates a generic object parameter.

openapi-generator version

v7.16.0 and up

OpenAPI declaration file content or url

 "/api/v1/example": {
	"put": {
		"operationId": "PutExample",
		"requestBody": {
			"required": true,
			"content": {
				"application/json": {
					"schema": {
						"type": "object",
						"examples": [
							{
								"example_key1": "value1",
								"example_key2": true
							}
						],
						"additionalProperties": true
					}
				}
			}
		},
		"responses": {
			"201": {
				"description": "Success (Created)"
			},
			"default": {
				"$ref": "#/components/responses/ErrorResponse"
			}
		}
	}
}

Generation Details

Command line:
java -jar openapi-generator-cli.jar generate -i swagger.json -g aspnetcore -o ./out -c generator.config.json

generator.config.json:

{
  "additionalProperties" : {
    "generateBody": false,
    "classModifier": "abstract",
    "nullableReferenceTypes": true,
    "operationResultTask": true,
    "aspnetCoreVersion": "8.0",
    "buildTarget": "library",
    "isLibrary": true,
    "useSwashbuckle": false
  }
}

Steps to reproduce

Using the openapi file + config listed above, the following method signature is generated on 7.16.0 and later:

[HttpPut]
[Route("/api/v1/example")]
[Consumes("application/json")]
[ValidateModelState]
[ProducesResponseType(statusCode: 0, type: typeof(Error))]
public abstract Task<IActionResult> PutExample([FromBody] object body);

The "addtionalproperties": true is supposed to generate a Dictionary parameter as was the case in 7.15 and earlier.

[HttpPut]
[Route("/api/v1/example")]
[Consumes("application/json")]
[ValidateModelState]
[ProducesResponseType(statusCode: 0, type: typeof(Error))]
public abstract Task<IActionResult> PutExample([FromBody]Dictionary<string, Object> requestBody);

Related issues/PRs

Potentially related?:

#22049

Suggest a fix

Use the supplied OpenAPI declaration, generator.config.json, and Java CLI command to reproduce output with the aspnetcore generator on v7.16.0 and compare it with v7.15. Inspect the handling of an object schema with additionalProperties: true. Done means the generated PutExample signature uses Dictionary<string, Object> as it did in v7.15 and earlier.