Phase 3

For phase 3 we want to start implementing the close command. We'll get the tar part working but not worry about encryption yet.

Make a new method perform on DrawerOperation which takes &self and returns Result<(), DrawerError>.
perform should first call validate and return the error if there is one.
After that, it should call either open(&self) or close(&self) depending on the operation type. For now, open will just be a todo!()
The new close method should create a vec consisting of the contents of the target directory as a tarball (use the tar create we depend on)
After creating the vec, it should write it out to the drawer file path.

I'm going to add some test data to the project under tests/ but it's just random data to test, ignore the contents of all those files.

Phase 3a

As a minor improvement, make the perform_close method also gzip the contents of the tarball.