chore: move executable code to src/

src/ now contains all source code - in subdirectories, according to the
.cabal component they belong to. This will allow us to put vendored
libraries in the same place - and later split our own code into multiple
components/libraries as well.

src/library/PostgREST/Response/GucHeader.hs

@@ -0,0 +1,30 @@
+module PostgREST.Response.GucHeader
+  ( GucHeader
+  , unwrapGucHeader
+  ) where
+
+import qualified Data.Aeson           as JSON
+import qualified Data.Aeson.Key       as K
+import qualified Data.Aeson.KeyMap    as KM
+import qualified Data.CaseInsensitive as CI
+
+import Network.HTTP.Types.Header (Header)
+
+import Protolude
+
+
+{-|
+  Custom guc header, it's obtained by parsing the json in a:
+  `SET LOCAL "response.headers" = '[{"Set-Cookie": ".."}]'
+-}
+newtype GucHeader = GucHeader (CI.CI ByteString, ByteString)
+
+instance JSON.FromJSON GucHeader where
+  parseJSON (JSON.Object o) =
+    case KM.toList o of
+      [(k, JSON.String s)] -> pure $ GucHeader (CI.mk $ toUtf8 $ K.toText k, toUtf8 s)
+      _ -> mzero
+  parseJSON _ = mzero
+
+unwrapGucHeader :: GucHeader -> Header
+unwrapGucHeader (GucHeader (k, v)) = (k, v)