Have a protocol of who accepted or declined a training and when. Use case: we play with friends only, no official matches, thus we only use the trainings. If we are not enough (we play 5 vs. 5 indoors), we cancel. Sometimes there is a hiccup and there is one decline too much last minute and it's always a problem to find out who was the **** who declined last minute ;) would be nice to have some kind of protocol or audit log for this.