Support PATCH for /allImages

[donaldgray]

See RFC-019 for more info.

Add PATCH support for /customers/{c}/allImages, accepting payloads in format:

{
 "member": [ {"id": "1/2/a"},{"id": "1/2/b"} ],
 "field": "manifests",
 "operation": "add|remove|replace",
 "value": [ "m123" ]
}

• "members" is the list of image ids to apply PATCH to
• "field" specifies which field is being modified - manifests is the only valid value for now (400 if other field)
• "operation" can be one of (400 if other value):
  • 'add' - add the specified value(s) to field
  • 'remove' - remove the specified value(s) from field
  • 'replace' - replace the field with specified value(s). null is rejected with 400 as need to be explicit, use [] to clear values.
• "value" is the value(s) to add/remove/replace

Returning HydraCollection of images. If no images found return an empty HydraCollection.

Writes should be atomic - competing requests that come in at the same time should both be recorded in the database. See npgsql EF support for arrays and RFC-019#implementation-details

Optional:

• If possible the implementation of this should be fairly dynamic to make it easier to extend operations and fields in the future