trusted-updates: signed statements that an update is ours.

  /root.json                         the root public keys
  /<product>/keys.json               which keys sign which channel (signed by a root key)
  /<product>/<channel>.json          a channel's current artifacts (signed by its key)
  /<product>/history/index.json      every document ever signed for the product

The format: docs/format.md in innonova/trusted-updates.