Remove participant from project

Removes the specified participant from the project. This does not delete the identity from the Identities service. If the corresponding identity is deleted from the Identity service, an event is generated and any associated participants are deleted. Since a project must have at least one owner, the last owner cannot be deleted. It is possible that the last owner could be removed if the corresponding identity is deleted from the Identities service. The project would be visible only to administrators who can delete the project or add a new owner.