### Steps to reproduce

1. Add a participants via the API

2. Try to delete a participant via the API


### What is the buggy behavior?

* There is no way to do so

* Sending a list with less participants (in an attempted workaround) results in a 500 due to the remaining duplicated participants (ie, those present as participants initially, and still in the updated shorter participants list being sent)


### What is the expected behavior?

1. There should be a way to remove participants via the Begin of the insertionAPI, by sending an updated list with fewer participantsEnd of the insertion Begin of the deletion APIEnd of the deletion