Do not do table count when plurality=singular

Rebasing commits by @ruslantalpa

src/PostgREST/ApiRequest.hs

@@ -130,7 +130,7 @@ userApiRequest schema req reqBody =
   , iPayload = relevantPayload
   , iPreferRepresentation = representation
   , iPreferSingular = singular
-  , iPreferCount = not $ hasPrefer "count=none"
+  , iPreferCount = not $ singular || hasPrefer "count=none"
   , iFilters = [ (k, fromJust v) | (k,v) <- qParams, k `notElem` ["select", "order"], isJust v ]
   , iSelect = if method == "DELETE"
               then "*"
@@ -145,7 +145,11 @@ userApiRequest schema req reqBody =
   hdrs            = requestHeaders req
   qParams         = [(cs k, cs <$> v)|(k,v) <- queryString req]
   lookupHeader    = flip lookup hdrs
-  hasPrefer val   = any (\(h,v) -> h == "Prefer" && v == val) hdrs
+  hasPrefer :: T.Text -> Bool
+  hasPrefer val   = any (\(h,v) -> h == "Prefer" && val `elem` split v) hdrs
+    where
+        split :: BS.ByteString -> [T.Text]
+        split = map T.strip . T.split (==';') . cs
   singular        = hasPrefer "plurality=singular"
   representation
     | hasPrefer "return=representation" = Full