The documentation explains Many<T> relations implemented as owned,
aggregated or embedded relationships.
But how do I implement an unowned one-to-many relation?
In GAE, this implemented by storing a List<Key> objects in the parent
object. The child object represented by a Key has its own lifecycle.
In Siena I can't use
- owned -> because it requires a link from the child to the parent back
- aggregated -> because child and parent are one entity group and the child
- embedded -> because i can't query this structure natively in GAE because
it is represented as a YAML string.