The Index Controller provides a save action to create or update a model.

The jsonSave action requires the id of the record that should be updated
to be given. If the id is 0 or not given at all a new item is created.

Every additional given parameter is mapped to the equal colum name of the
item. Before adding or updating the item, the data is validated. If an error occurs
an PublishedException is thrown, which can be caught by the Dojo clinet.

The structure of such a json serialized exception is described in the Interals/Concepts/Exceptions
chapter of the documentation.