model: Uniqueness checks are not functional

Referable.update_from() patches the self object with the other object by iterating over the attributes of the other objects using the python built-in vars(). vars() only iterates over an objects attributes, not properties e.g. getter/setter functions. The id_short attribute of Referable is a property, which performs additional checks when setting the id_short, such as checking for uniqueness within the namespace by searching the objects contained in the parent object. The actual value of the id_short is stored in the protected attribute _id_short.
Since _id_short is an attribute and id_short is a property, the vars() built-in returns the _id_short attribute instead of the id_short property, which causes update_from() to update the _id_short directly, skipping the setter function and thus the uniqueness check. This is also the case for the semantic_id property of HasSemantics, which also checks for uniqueness.

A solution proposed by @sebastian.heppner and @mhthies is to add dictionaries to each class, mapping the protected attributes to the respective property. These dictionaries would then be searched by update_from(), which can then set the property instead of the attribute.

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Another issue is that this uniqueness check is not performed for objects contained in one or more AbstractObjectStore, because these are not referenced by the parent attribute.

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The third and final issue is located in NamespaceSet.update_nss_from(). [...]

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Each fix has to be backported to the not yet existent V2.0 branch.

Progress Tracker:

• Uniqueness not checked in Referable.update_from()
• No uniqueness check for objects inside an AbstractObjectStore
• NamespaceSet.update_nss_from()