The MongoDB upstream developers dropped the mongoclient library in favor of https://github.com/mongodb/mongo-cxx-driver This has been reported in Debian here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=833055

I think you need to adjust your codebase to work with mongo-cxx-driver or another client library. Unfortunately in Debian, mongo-cxx-driver is not yet available. But there are other MongoDB client libraries too starting with the plain C version. Do we really need a C++ library?