Add part4

part4/src/Data/AuthToken.elm

@@ -0,0 +1,31 @@
+module Data.AuthToken exposing (AuthToken, decoder, encode, withAuthorization)
+
+import HttpBuilder exposing (RequestBuilder, withHeader)
+import Json.Decode as Decode exposing (Decoder)
+import Json.Encode as Encode exposing (Value)
+
+
+type AuthToken
+    = AuthToken String
+
+
+encode : AuthToken -> Value
+encode (AuthToken token) =
+    Encode.string token
+
+
+decoder : Decoder AuthToken
+decoder =
+    Decode.string
+        |> Decode.map AuthToken
+
+
+withAuthorization : Maybe AuthToken -> RequestBuilder a -> RequestBuilder a
+withAuthorization maybeToken builder =
+    case maybeToken of
+        Just (AuthToken token) ->
+            builder
+                |> withHeader "authorization" ("Token " ++ token)
+
+        Nothing ->
+            builder