Caching: node class is not taken into account making subclasses potentially indistinguishable

[sphuber]

As reported here aiidateam/aiida-quantumespresso#1015
Two data nodes of different classes, but where one is a subclass of the other, will have an identical hash as long as the attributes are the same. This is because Node._get_objects_to_hash does not include the class itself, which it arguably should.

[sphuber]

Example:

In [1]: from aiida.orm import Data, Int

In [2]: i = Int(5).store()

In [3]: d = Data()

In [4]: d.base.attributes.set('value', 5)

In [5]: d.store()
Out[5]: <Data: uuid: 8644cb29-497a-42d8-b723-e895cf30ea56 (pk: 157610)>

In [6]: i.base.caching.get_hash() == d.base.caching.get_hash()
Out[6]: True

This is true because Int is a subclass of Data, but arguably the hashes should be different.