Release notes

Enhancements

• Added OhlcvEod variant to RType
• Added documentation to more enums and record structs
• Aligned string representation of RType with Rust

Breaking changes

• Switched to std::byte for most padding fields in record structs. These fields are
  now initialized by default
• Hidden padding fields now begin with _

Bug fixes

• Added missing IndexTs() method to v1::InstrumentDefMsg, v2::InstrumentDefMsg,
  and v1::SymbolMappingMsg
• Fixed error in templated overload of DbnDecoder::EncodeRecord()
• Removed unused Disk and S3 variants from Delivery enum