Add support for Process classes to QueryBuilder.append

[sphuber]

If I have the CalcJob class PwCalculation, which has entry point aiida.calculations:quantumespresso.pw, calling QueryBuilder.append(PwCalculation).all() should tell the query builder to return all nodes that have a type string node.process.calculation.calcjob.CalcJobNode. and a process_type string aiida.calculations:quantumespresso.pw. This is essentially an AND statement of these two values. Note that since append supports adding tuples of classes, e.g. QueryBuilder.append((PwCalculation, ArithmeticAddCalculation)), this should be unwrapped into two sub filters that are OR'ed, i.e. in pseudo SQL

        WHERE (
            type = 'node.process.calculation.calcjob.CalcJobNode.' AND
            process_type = 'aiida.calculations:quantumespresso.pw'
        ) OR (
             type = 'node.process.calculation.calcjob.CalcJobNode.' AND
             process_type = 'aiida.calculations:arithmetic.add'
        )

technically since the process_type should also support querying for sub classes, the filter on process type should be an OR of process_type = 'aiida.calculations:quantumespresso.pw' and process_type like 'aiida.calculations:quantumespresso.pw.'

[ltalirz]

Just to summarize the logic here:

• parameter cls: need to provide a class:

  • if an instance is provided (instead of a class), raise an exception
  • if Process class is provided, get corresponding Node class and filter by its type (as well as the process_type)
  • if Node class is provided, just use its type for filtering.
  • if a tuple of classes is provided, use combination logic mentioned in the issue description

• parameter type: we would need to add an additional parameter process_type. At this point, the question arises whether we really need to have both type and process_type as parameters. Should they just be replaced by filters instead?
  @lekah mentions that type was added just for the REST API. This would indicate that it can simply be replaced by corresponding filters

• parameter subclassing: if True, include subclasses both of type and process_type (if used to filter).

[sphuber]

Fixed in PR #2421