Write example that finds J^PC numbers with CSPSolver directly

[redeboer]

As a step towards #219 and #20 (and an alternative to #266), it would be a good exercise to generate all allowed $J^{PC}$ numbers (spin, parity, $C$ parity) in a three-body decay using the CSPSolver directly (or if needed, using python-constraints directly). It's essentially reproducing the steps from the STM for a limited number of quantum numbers, without using a particle database.

Sub-tasks

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1. Try at first to just use the STM-Method for the generation of the QNProblemSet
2. Create self.__allowed_intermediate_states (particles = load_pdg() -> create_edge_properties() -> GraphEdgePropertyMap)
3. Test CSPSolver.find_solutions() on QNProblemSet directly
4. Limit available edge properties + settings in QNProblemSet
5. Optional: Find where CSPSolver introduces spin-projections

An example from the visualization tutorial, $\psi^\prime \to \gamma \eta \eta$, i.e. $1^{--} \to 1^{--},0^{+-},0^{+-}$:

Particle transitions

[redeboer]

Looking through the code for the STM, I found that the only place where CSPSolver is called is in the _solve() method of the STM:

qrules/src/qrules/transition.py

Lines 648 to 651 in 9d2bb7c

	def _solve(self, qn_problem_set: QNProblemSet) -> tuple[QNProblemSet, QNResult]:
	solver = CSPSolver(self.__allowed_intermediate_states)
	solutions = solver.find_solutions(qn_problem_set)
	return qn_problem_set, solutions

In the documentation, the closest thing to _solve() is find_quantum_number_transitions(), which is described here:
https://qrules.readthedocs.io/0.10.x/usage/visualize.html#quantum-number-solutions

It seems to me you have to formulate a limited form of a ProblemSet (only spin, parity and c_parity plus the relevant conversation rules. Maybe that tutorial shines some light on it 😬