Shielding transactions should be reported as such

[AArnott]

A shielding transaction appears in the history as simply a spend in the amount of the transaction fee.

This code looks responsible for that:

https://github.com/zingolabs/zingolib/blob/273263290c07469c34ae0db578a8f694e2df8e0e/zingolib/src/lightclient.rs#L1879-L1881