Currently, to create an owning bson_value::value, users must first construct a bsoncxx::document::value, then parse out the bson_value they are interested in:

auto doc = make_document(kvp("v", some_value));

auto owning_value = doc.view()["v"].get_owning_value();

Let's provide a variadic helper function like the make_document and kvp helpers to facilitate this.