Task status

Tasks can have four different status as agreed on https://os2web.atlassian.net/browse/VALGHAL-124

• Missing: Task has ParticipantId is null.

• Awaiting: Task has ParticipantId not null and Responsed = false.

• Assigned: Task has ParticipantId not null and Responsed = true & Accepted= true

• Rejected: Task has ParticipantId not null and Responsed = true & Accepted= false.