Handle overloaded function case

* Add test for params=single-object on GET

* Add tests for procs with DEFAULT args

* Add tests for overloaded functions

* Add test for PATCHing with an empty json array, this previously
  gave a "Something is wrong" error

src/PostgREST/Parsers.hs

@@ -47,12 +47,6 @@ pRequestLogicTree (k, v) = mapError $ (,) <$> embedPath <*> logicTree
     -- Concat op and v to make pLogicTree argument regular, in the form of "?and=and(.. , ..)" instead of "?and=(.. , ..)"
     logicTree = join $ parse pLogicTree ("failed to parse logic tree (" ++ toS v ++ ")") . toS <$> ((<>) <$> op <*> pure v)
 
-pRequestRpcQParam :: (Text, Text) -> Either ApiRequestError RpcQParam
-pRequestRpcQParam (k, v) = mapError $ (,) <$> name <*> val
-  where
-    name = parse pFieldName ("failed to parse rpc arg name (" ++ toS k ++ ")") $ toS k
-    val = toS <$> parse (many anyChar) ("failed to parse rpc arg value (" ++ toS v ++ ")") v
-
 ws :: Parser Text
 ws = toS <$> many (oneOf " \t")