 access all available @categories@ from /config.yaml/.
         -> Int         -- ^ 'Category' at level @n@ in /config.yaml/.
         -> Course      -- ^ First 'Table' row to compare.
         -> Course      -- ^ Second 'Table' row to compare.
         -> Bool        -- ^ 'True' if the two rows have the same 'Category' 'Text'.
catGroup cnf n = (==) `on` catAt cnf n


{- | Returns the value of the fir
catGroup :: Config      -- ^ Used to access all available @categories@ from /config.yaml/.
         -> Int         -- ^ 'Category' at level @n@ in /config.yaml/.
         -> Course      -- ^ First 'Table' row to compare.
         -> Course      -- ^ Second 'Table' row to compare.
         -> Bool
catGroup cnf n = (==) `on` catAt cnf n
catGroup cnf n = (==) `on` catAt cnf n