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

[devhl-labs]

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;
}

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