mongocxx::instance is under-documented and difficult to use correctly. We should make the following improvements to our documentation of mongocxx::instance:

• The mongocxx "Quick Start" page under "Tutorial for mongocxx" does not mention mongocxx::instance. We should add a section which explains what mongocxx::instance is, and also makes a recommendation to users on how to manage this object.
• All mongocxx examples should contain a code comment indicating that creating a mongocxx::instance object is necessary to initialize the driver.
• The class comment for instance.hpp should be expanded. In particular, it should:
  • Indicate explicitly that the mongocxx::instance constructor initializes the driver and that mongocxx::instance destructor shuts down the driver.
  • Explain that instantiating mongocxx::instance more than once in the same program is an error (even if the objects have non-overlapping lifetimes).
  • Contain a short example of basic correct usage of mongocxx::instance.
  • Contain an example of common incorrect usage of mongocxx::instance.
  • Refer users to the "instance_management" example for advanced mongocxx::instance usage.