Immutable documents

There are cases where a document should be made not modifiable, for example, if the document is very important and should not be lost or canceled for any reason.

An immutable document can not be altered so:


 * it's metadata are not modifiable
 * it cannot be moved to another folder
 * it cannot be restored from the GUI
 * only accredited users can mark the document as immutable.
 * on each folder the Administrator can give documents immutability permission to a specific groups of users.

We implement this feature with a boolean flag on each document that determines if it is immutable or not. In the GUI, immutable documents are recognizable by an icon and a special mark.