Add depth constraint to Root
To better emulate GnuPG's trust model, while at the same time being able to implement Sequoia's trust model on the same dataset, it would be convenient to constrain the maximal length of paths starting from GnuPG's trust roots, while not constraining paths from Sequoia's trust root.
I added https://docs.rs/sequoia-wot/latest/sequoia_wot/struct.QueryBuilder.html#method.maximum_depth but that constraints the search globally, i.e. it also affects paths from Sequoia's root.
I think we could add a constraint to Root
and check it during back-propagation, right?