I'm using the rest API POST /rest/servicedeskapi/request to create service desk tickets. We have some customers in our system with "legacy" usernames (test@example.com) and others with newer usernames (qm:3Bc26d3302-3729-453e-96cd-f76f2fa3d0a7:3A5ad4da29924ac92a7c0dc3c7). We've noticed that anytime we try to create a request with a new username in the requestParticipants field, we always get back an error: "Sorry, but the following usernames could not be added as participant to this request". This API works fine without requestParticipants, and when it has only "legacy" username requestParticipants. Why do the new usernames seem to be causing issues?