feature: add a method to distinguish between "trusted" values and "untrusted" values. #237
Description
Right now, when serializing statements, we assume that every value in the statement could be untrusted and should be escaped. In practice, this is not necessarily true. We should investigate if there is a way to track untrusted values through the system.
Exploration is needed to find prior art and to decide if doing this is actually a good idea.