mostly #7524 and #7413 so that "cancellations" of shift and shift_templates work fine especially when adding/changing shift

take into account the possibility of several shift_template_registration for one res_partner, but only one active

code cleaning : get rid of quick-and-dirty circular dependency fix by moving some code in separated file

#7426 : remove suspicious code introduced in v12 port and updating makeups_to_do inside a getter method

#7422 : change variable names in delete_pair_core and use suppleant_member_id to find member to unsubscribe instead of email matching

#7325 : use suppleant_member_id instead of parent_id or is_associated_people to perform binom checks