message: c# core: Add documentation for untagged bonded.
diff: key, mapped each item encoded according to its type
  + .-------. .-----------.
  + bonded | count | | marshaled |
  + '-------' '-----------'
  + count uint32 count of bytes (always fixed-width, even in v2)
  +
  + marshaled a marshaled payload
  +
  */
  #endregion
  