Ability to automatically create IDs from content hash of row

[simonw]

Sometimes when you are importing data the underlying source provides records without IDs that can be uniquely identified by their contents.

A utility mechanism for calculating a sha1 hash of the contents and using that as a unique ID would be useful.

[simonw]

Example: http://api.nobelprize.org/v1/laureate.json

This includes affiliations which look like this:

      "affiliations": [
        {
          "name": "Sorbonne University",
          "city": "Paris",
          "country": "France"
        }
      ]