[BUG] [csharp] OpenAPI generator fails create nullable array items

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

I have such a component in swagger.json (openapi version: "3.0.1")

      "testNullable": {
        "type": "array",
        "items": {
          "type": "string",
          "format": "uuid",
          "nullable": true,
          "x-nullable": true
        },
        "nullable": true,
        "x-nullable": true
      }

With OpenAPI generator, I intend to create such a type in C#:
List<Guid?>?
However, as a result, it generates
List<Guid>?
I traced the models, to find the dataType as follows (datatypeWithEnum with the same value):

"dataType" : "List<Guid>", 
"datatypeWithEnum" : "List<Guid>"

and IsNullable is true
"isNullable" : true
For its items, the dataType is Guid and isNullable is true

"dataType" : "Guid",
"datatypeWithEnum" : "Guid",
"isNullable" : true,

The mustache statement is
{{{datatypeWithEnum}}}{{#lambda.first}}{{#isNullable}}{{>NullConditionalProperty}}...
So we can tell that the '?' actually comes from NullConditionalProperty.

Question: Is it supported that the array items can be nullable for C# language generator?

It seems to be specifically avoided for generichost libaray. Is there any reason? How can I work it around? @devhl-labs

openapi-generator version

openapi-generator-cli-7.12.0.jar

OpenAPI declaration file content or url

https://gist.github.com/jasonxu08/40d66713fba773e3903e95140e71f29f

Generation Details

java -jar openapi-generator-cli-7.12.0.jar generate -g csharp -i "./weather.json" -o "src/w1/" -c "./config.yaml" --additional-properties="packageName=testWeather,targetFramework=net8.0,nullableReferenceTypes=true,library=generichost,validatable=false,optionalEmitDefaultValues=true"

Steps to reproduce

Save the swagger description to 'weather.json' and run the generation command.

Related issues/PRs

Suggest a fix

In this case, I suppose that the nullable mark (?) should be contained with datatypeWithEnum or any other property.

Reproduce the issue using the linked OpenAPI example as weather.json, config.yaml, and the provided csharp generation command. Start by tracing how datatypeWithEnum and isNullable are handled for array items and the NullConditionalProperty mustache statement; done means the generated type represents the nullable array items as List<Guid?>?.