fix: [API] massive performance boost for large events with many correlations
fix: [API] massive performance boost for large events with many correlations

- the logic of the JSON converter was heavy and unnecesary

FIRSTdotorg/MISP,FIRSTdotorg/MISP,MISP/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,FIRSTdotorg/MISP,MISP/MISP,MISP/MISP,MISP/MISP,SteveClement/MISP,FIRSTdotorg/MISP,SteveClement/MISP,SteveClement/MISP