Make the registration switch work again

src/Vervis/Foundation.hs

@@ -544,9 +544,24 @@ instance YesodAuthAccount AccountPersistDB' App where
     passphraseResetKeyDuration _ = Just $ fromTimeUnit (1 :: Day)
     allowLoginByEmailAddress _   = True
     runAccountDB                 = unAccountPersistDB'
-    unregisteredLogin u          = do
+
+    unregisteredLogin u = do
         setUnverifiedCreds True $ Creds "account" (username u) []
         return mempty
+    registrationAllowed = do
+        settings <- getsYesod appSettings
+        if appRegister settings
+            then do
+                room <- case appAccounts settings of
+                    Nothing -> return True
+                    Just cap -> do
+                        current <- runDB $ count ([] :: [Filter Person])
+                        return $ current < cap
+                return $
+                    if room
+                        then Nothing
+                        else Just $ setMessage "Maximal number of registered users reached"
+            else return $ Just $ setMessage "User registration disabled"
 
 -- This instance is required to use forms. You can modify renderMessage to
 -- achieve customized and internationalized form validation messages.