When w is -2 (libmongoc's default), our debug handler hides rendering of other fields in the debug output. This is especially problematic because explicitly providing w=1 to libmongoc (e.g. in URI options) results in -2 being stored. I assume the current behavior was added by thinking MONGOC_WRITE_CONCERN_W_DEFAULT meant the entire write concern was defaulted (not just w).

It would be more straightforward if we always print all fields. Additionally, I think we can still render w as "majority" alongside our synthetic wmajority boolean field, since that is the actual value being passed in w. Users can still rely on our boolean to avoid a string comparison check.