start transition to multiple variants per submission

Handler/ShowChallenge.hs

@@ -302,6 +302,7 @@ outForTest repoDir submissionId (Entity testId test) = do
   checksum <- liftIO $ gatherSHA1ForCollectionOfFiles [outF]
   return Out {
     outSubmission=submissionId,
+    outVariant=Nothing,
     outTest=testId,
     outChecksum=SHA1 checksum }
 

config/models

@@ -59,6 +59,10 @@ Submission
     isPublic Bool default=False
     isHidden Bool Maybe
     UniqueSubmissionRepoCommitChallenge repo commit challenge
+Variant
+    submission SubmissionId
+    name Text
+    UniqueVariantSubmissionName submission name
 Fork
     source SubmissionId
     target SubmissionId
@@ -77,6 +81,7 @@ Comment
     text Textarea
 Out
     submission SubmissionId
+    variant VariantId Maybe
     test TestId
     checksum SHA1
     UniqueOutSubmissionTestChecksum submission test checksum