Potential issues in the partial evaluation logic

https://github.com/Joffref/cedar/blob/7ec84fa85f69094d9df2048dc95cff06ad625f58/lib/src/interface.rs#L63

The only way I got partial evaluation to work was to use Request::RequestBuilder since you might be missing the principal, action, or resource. I don't mind sharing my code, but I'm sure my code is horrific since this is the first time I write any Rust code.

https://github.com/Joffref/cedar/blob/7ec84fa85f69094d9df2048dc95cff06ad625f58/lib/src/interface.rs#L66

I also had to convert the entity store into a partial evaluation compatible one using Entities::partial