For some IDL generated classes, it is desirable to differentiate between the field names in BSON and the names in the generated C++ code. A good example of this is oplog entries which use one and two letter field names to keep the BSON small but may desire for the code to have a more verbose description of a field.

Example:

    demo_struct:
        fields:
            o:
                type: int
                cpp_name: operation

Instead of generating:

std::int32_t getO() const;
void setO(std::int32_t value) const;

more descriptive names will be used instead.

std::int32_t getOperation() const;
void setOperation(std::int32_t value) const;

Reported by judah.schvimer