todo.MD

TODOs

• bson.hpp
  • migrate to absl::variant or boost::variant2
• index.hpp
  • add overload to compound_index's lookup taking span<non_null_ptr<bson const>>
• index_manager.hpp
  • add lookup functionality
  • check compoun_index's insertion policy if all field must be present?
• cursor.hpp
  • add compile time value getting largest possible cursor size
• collection.hpp
  • change document vector to use std::unique_ptr<document>
  • refactor insertion API
    • take entire documents
    • take functors?
• TESTS!!!