faux: enable for other fields than "serial"

[TobiasKadelka]

I do not see any specific reason, why we should enable the random string generation only for serial numbers.
This makes sense in our specific use case, of course, but there might be other use cases out there.

This is IMO especially relevant since we allow the name schemes for assets to be any type of string, containing different keys than "type, make, model, and serial", as for example described in "Inventory variations #375".