[BUG] CodegenProperty IsDecimal is not true when DataType == "decimal"

Please see the lengthCm property in
spec:
modules/openapi-generator/src/test/resources/3_0/csharp/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
sample:
samples/client/petstore/csharp-netcore/OpenAPIClient-generichost-net6.0

I have added this as a hotfix, but perhaps it should not be needed:
modules\openapi-generator\src\main\java\org\openapitools\codegen\languages\AbstractCSharpCodegen.java

if (property.datatypeWithEnum.equals("decimal")) {
    property.isDecimal = true;
}

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• 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?
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Description

openapi-generator version

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

Start with modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java and inspect how the lengthCm property is represented from spec/modules/openapi-generator/src/test/resources/3_0/csharp/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml. Compare the generated samples/client/petstore/csharp-netcore/OpenAPIClient-generichost-net6.0 output with the expected decimal handling; done means IsDecimal is correctly true without relying on the reported hotfix.