Temporary: make /version show request headers

So I can debug HTTPS termination.

src/Handlers.hs

@@ -29,6 +29,7 @@ import           Calendar
 import           Control.Monad.Trans.Maybe
 import           Data.FileEmbed            (embedFile)
 import qualified Data.SortedList           as SL
+import qualified Network.Wai
 import           Development.GitRev
 import Data.Time.Zones (localTimeToUTCTZ, utcToLocalTimeTZ)
 import qualified FreshCache                as FC
@@ -142,5 +143,7 @@ getRobotsR =
   return $ TypedContent typePlain $ toContent $(embedFile "config/robots.txt")
 
 getVersionR :: Handler Text
-getVersionR =
-  return $ $(gitHash) <> if $(gitDirty) then "+" else ""
+getVersionR = do
+  req <- reqWaiRequest <$> getRequest
+  let hs = foldMap (\(h,v) -> tshow h <> ": " <> tshow v <> "\n") $ Network.Wai.requestHeaders req
+  return $ hs <> "\n" <> $(gitHash) <> if $(gitDirty) then "+" else ""