create "itest-user" and send him to preserved
try to add the same user again (should fail)
restore "itest-user" user
add already existing user "itest-user" to stage and try to activate the latter (should fail)
delete "itest-user" staged user
add "itest-user2" and send him to staged (through preserved)
add new "itest-user2" - one is already staged (should pass)
send active "itest-user2" to preserved
try to activate staged "itest-user2" while one is already preserved (should fail)
delete preserved "itest-user2" and activate the staged one (should pass)