Include historical currency codes

[jbransen]

Currently the package includes only 'active' currencies, but ISO 4217 used to contain other codes as well (i.e. BYR, which was removed in 2016), which we still may want to parse and/or represent in systems dealing with old payment information. It would be nice to include those as well, maybe with some sort of checking function stating that it is outdated.

[KtorZ]

This information could be encoded in the type representation itself ?

-- | Actual representation of a currency
data Currency = Currency
  { alpha   :: Alpha -- ^ Alpha Code
  , numeric :: Int   -- ^ Numeric code
  , minor   :: Int   -- ^ Number of decimal units
  , name    :: Text  -- ^ English name
  , active  :: Bool  -- ^ True if the currency is still in circulation
} deriving (Show, Eq, Read, Generic, Data, Typeable)

[jbransen]

Right, of course!

[KtorZ]

I'll spend a bit of time on #2 tomorrow. I'll see if I can tackle this #3 after.