Update Manifest w/ paintedResources (MVP)

[donaldgray]

See RFC https://github.com/dlcs/iiif-presentation/blob/main/docs/rfcs/0002-manifest-write-mvp.md

RFC outlines how MVP update functionality will work. This is for PUT requests with "paintedResources" on api/flat path only (ie no hierarchical path updates OR "items" handling).

Rather than diff the incoming and existing payloads the manifest will be recreated each time, as if it were new - so "update" is effectively "recreate", with the caveat that we must maintain the public view of the manifest.