Tcases for OpenAPI doesn't support generator definitions

[kerrykimbrough]

When you are using Tcases for OpenAPI, you are not creating the input model for your API directly. Instead, it is generated automatically from your OpenAPI definition. That makes it hard to know the input variable names, which is necessary if you wanted to create a tuple generator definition. For that reason, Tcases for OpenAPI doesn't support generator definitions, so only the default 1-way coverage is possible.

Thanks to @ClayGminx for pointing out this shortcoming.