Handle Batch Errors

[donaldgray]

Warning

Blocked by dlcs/protagonist#936

This ticket outlines what happens if a batch encounters an error. The overall process is:

• Continue to process the manifest and save it to S3,
• Requests for the public or API version of the manifest should return a 200 as we generated the manifest.
• For API responses the "error" property of assets will outline which assets encountered failed.
• The IIIF manifest will carry a "seeAlso" block to highlight any errors

dlcs/protagonist#936 adds a "seeAlso" error to any canvases that contain an erroring asset. We need to ensure that the error survives any canvas manipulation and ends up on:

• The "canvas" element, if it's 1 image per canvas
• OR the content resource if it's multiple images per canvas (e.g. a choice, sample json below):

"items": [
    {
      "id": "..canvas..",
      "type": "Canvas",
      "items": [
        {
          "id": "..annopage..",
          "type": "AnnotationPage",
          "items": [
            {
              "id": "..anno..",
              "type": "Annotation",
              "motivation": "painting",
              "body": {
                "type": "Choice",
                "items": [
                  {
                    "id": "../iiif-img/1/2/image-with-error/.../default.jpg",
                    "type": "Image",
                    "format": "image/jpeg",
                    "service": [...],
                    "seeAlso": "**error-from-nq**"
                  },
                  {
                    "id": "../iiif-img/1/2/image-without-error/.../default.jpg",
                    "type": "Image",
                    "format": "image/jpeg",
                    "service": [...]
                 }
            }
        }
   }
]

NQs in any deployed environment will need to be updated with new NQ configuration - this will need to be highlighted in release notes somehow. The example NQ in readme.md should be updated too.