Instance Codex RAML and JSON v1

Purpose: To implement the first pass at the instance Codex record so we have the object established in FOLIO. We are starting with the simplest metadata for the record (we selected elements that we were pretty certain were 1:1 with the record). The record's metadata will grow and evolve as we get more input from SMEs on what belongs.

NOTE: We might want to hold off on making the link between this new instance record and the item record we already have, as discussions are underway as to whether we need a "holdings record" in between (holdings records generally include the extent of holdings for multipart items (so coverage date ranges) and may also include location).

See this spreadsheet for the first pass set of metadata: https://docs.google.com/spreadsheets/d/1DlVQf8iJvt7maeImiX2KO-sD6jliXwnM6iU3bhyDIWA/edit#gid=1735594141. Only the items with UIIT-20 are in scope for this story.