OSIS-3515 Keep only common functions in EventPerm class + extract QS
OSIS-3515 Keep only common functions in EventPerm class + extract QS

uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis,uclouvain/osis,uclouvain/OSIS-Louvain