Do not assume that icfs:name is unique. Allow to specify uniqueness for any attribute (schemaHandling).
We need at least:
- Specify whether to check for uniqueness or not (for iteration)
- Specify whether the attribute is unique in the resource
- Specify whether the uniquiness applies to norm or orig values of polystrings (e.g. case insensitive or sensitive) - this is also related to case sensitive login names
- .... ?
We need flexible support for uniqueness in the repo. We need to be able to check uniqueness and create new object atomically. Also check for uniqueness and modify object atomically. This is needed for flexible uniqueness constraints in the model. But it is also needed to reliable create shadows without a risk of conflicts.