Add cds utils modelling

[knewbury01]

What This PR Contributes

This PR overall contributes models for the cds.utils CAP module, the implementation of which can be found here and the documentation here. Specifically the model is comprised of :

• sinks - functionality of the module that allows for file system manipulation (e.g. controlling which file is being read from or controlling which file is removed)
• additional flow steps - functionality of the module that take a potentially user controlled value and return some representation of that value that is sufficiently unaltered that a path traversal attack could occur

Future Works

The next step of this work will be to include a query that uses CAP specific sources and these sinks to describe the specific potential path traversal vulnerability that could occur through this API