chore: matriculation numbers limited same length again

- this time as suffixes
- also start range description with full used length
  otherwise suffix-description is confusing

src/Handler/Utils/Exam.hs

@@ -333,7 +333,8 @@ examAutoOccurrence (hash -> seed) rule config@ExamAutoOccurrenceConfig{..} occur
                    | (uid, (User{..}, Nothing)) <- Map.toList users
                    , matriculation' <- userMatrikelnummer ^.. _Just . filtered (not . null)
                    ]
-            in matrUsers
+               takeEnd n chars = drop (length chars - n) chars
+            in Map.mapKeysWith Set.union (takeEnd . F.minimum . Set.map length $ Map.keysSet matrUsers) matrUsers
       _ -> Map.singleton [] $ Map.keysSet users
 
     occurrences' :: Map ExamOccurrenceId Natural
@@ -599,10 +600,18 @@ examAutoOccurrence (hash -> seed) rule config@ExamAutoOccurrenceConfig{..} occur
                     && (null t || Just (toNullable nextStart) > maybeEnd)
                   = go nextStart borderLength ((occurrenceId, mappingDescription) : acc) t
                   | borderLength < maxTagLength
-                  = go (singleton $ head alphabet) (succ borderLength) [] result
+                  = go restartStart restartBorderLength [] result
                   | otherwise
                   = []
                   where
+                    restartBorderLength :: Int
+                    restartBorderLength = succ borderLength
+
+                    restartStart :: NonNull [CI Char]
+                    restartStart = case rule of
+                      ExamRoomMatriculation -> impureNonNull $ replicate restartBorderLength $ head alphabet
+                      _rule -> singleton $ head alphabet
+
                     mappingDescription :: Set ExamOccurrenceMappingDescription
                     mappingDescription = Set.fromList $ case maybeEnd of
                       (Just end) -> ExamOccurrenceMappingRange (toNullable start) end : specialMapping