Manifest PUT handles updates

[donaldgray]

If manifest has "items" - as-is

If has "paintedResources" the process is effectively a create (again) bearing in mind:

1. Batch history should be maintained
2. CanvasPainting rows in DB should reflect what we've just received.

Not sure how best to do (2) - something like the following might work, assuming PK values can easily be used to inform create/update/delete commands:

// get manifest with CanvasPaintings
var manifest = dbContext.Manifests.Include(m => m.CanvasPaintings).Single(m => m.Id = manifestId);

// replace CanvasPaintings
manifest.CanvasPaintings = theCanvasPaintingsFromPayload;

// let EF change tracking figure it out
dbContext.SaveChanges();