Support v3 AnnotationBody Services

[christopher-johnson]

Related to IIIF-Commons/manifesto#34, the current ExternalResource implementation here, does not expect an AnnotationBody to have a service as it returns the "id" by default. The method also assumes the presence of the v2.1 "images" property.

For reference, I am testing with Annotations that look like this:

{
  "id": "https://iiif.ub.uni-leipzig.de/0000005815/anno/e27bdd76-a3aa-4f5c-99a7-d3ff603718c3",
  "type": "Annotation",
  "motivation": "painting",
  "body": {
    "id": "https://iiif.ub.uni-leipzig.de/0000005815/00000451.jpg",
    "type": "Image",
    "format": "image/jpeg",
    "service": [
      {
        "id": "https://iiif.ub.uni-leipzig.de/iiif/j2k/0000/0058/0000005815/00000451.jpx",
        "type": "ImageService2",
        "profile": "level1"
      }
    ],
    "height": 5760,
    "width": 3840,
    "label": {
      "@none": [
        "2r mit Farbkeil"
      ]
    }
  },
  "target": "https://iiif.ub.uni-leipzig.de/0000005815/canvas/00000451"
}