Implement incoming/outgoing spins/pols correctly

Use multiplicity in averaging_norm of Compton
CI_UNIT_PKG_URL_QEDbase: https://github.com/AntonReinhard/QEDbase.jl#d2740177b1abe4ab2f5ca2693dd53ae307865024

src/processes/one_photon_compton/perturbative/cross_section.jl

@@ -21,8 +21,7 @@ end
     We average over the initial spins and pols, and sum over final.
 """
 function QEDbase._averaging_norm(proc::Compton)
-    normalizations = multiplicity.(_in_spin_and_pol(proc))
-    return inv(prod(normalizations))
+    return inv(incoming_multiplicity(proc))
 end
 
 @inline function _all_onshell(psp::PhaseSpacePoint{<:Compton})

src/processes/one_photon_compton/process.jl

@@ -36,14 +36,22 @@ _spins(proc::Compton) = (proc.in_spin, proc.out_spin)
 _in_spin_and_pol(proc::Compton) = (proc.in_spin, proc.in_pol)
 _out_spin_and_pol(proc::Compton) = (proc.out_spin, proc.out_pol)
 
-function QEDprocesses.incoming_particles(::Compton)
+function QEDbase.incoming_particles(::Compton)
     return (Electron(), Photon())
 end
 
-function QEDprocesses.outgoing_particles(::Compton)
+function QEDbase.outgoing_particles(::Compton)
     return (Electron(), Photon())
 end
 
+function QEDbase.incoming_spin_pols(proc::Compton)
+    return (proc.in_spin, proc.in_pol)
+end
+
+function QEDbase.outgoing_spin_pols(proc::Compton)
+    return (proc.out_spin, proc.out_pol)
+end
+
 function _spin_or_pol(process::Compton, ::Electron, ::Incoming)
     return process.in_spin
 end