Description
When a model contains a DateOnly and serialize to date (https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.0.md#data-types) the generated model contains a datetime and the DateTimeJsonConverter does not handle a date format. The deserialization throw a NotSupportedException.

I would suggest to serialize also as date. But it's up to the server converter to handle datetime as date.

openapi-generator version
6.3.0-20230125.125049-89

csharp-netcore

OpenAPI declaration file content or url
https://gist.github.com/kYann/23eab426be79fd2cb93c2ddb902a8ecd

"date": {
            "type": "string",
            "format": "date",
            "example": "2017-07-21"
          }

Generation Details
`java -jar ..\openapi-generator-cli-6.3.0-20230125.125049-89.jar generate -i ..\swagger.json -c ..\config.yaml``

config

generatorName: csharp-netcore
library: generichost
additionalProperties:
artifactId: PublicClient
packageName: PublicClient
targetFramework: net6.0
useDateTimeOffset: true
nullableReferenceTypes: true
packageDescription: Public client to access rest api
packageTitle: "Api Public Client"
Steps to reproduce
Run generate command on the provided swagger file.

Suggest a fix
Handle deserialization of date to datetime or directly handle generation of dateonly.