Update part3

advanced/part3/src/Viewer/Cred.elm

@@ -1,4 +1,20 @@
-module Viewer.Cred exposing (Cred, addHeader, addHeaderIfAvailable, decoder, encodeToken)
+module Viewer.Cred exposing (Cred, addHeader, addHeaderIfAvailable, decoder, encodeToken, username)
+
+{-| The authentication credentials for the Viewer (that is, the currently logged-in user.)
+
+This includes:
+
+  - The cred's Username
+  - The cred's authentication token
+
+By design, there is no way to access the token directly as a String.
+It can be encoded for persistence, and it can be added to a header
+to a HttpBuilder for a request, but that's it.
+
+This token should never be rendered to the end user, and with this API, it
+can't be!
+
+-}
 
 import HttpBuilder exposing (RequestBuilder, withHeader)
 import Json.Decode as Decode exposing (Decoder)
@@ -7,14 +23,30 @@ import Json.Encode as Encode exposing (Value)
 import Username exposing (Username)
 
 
+{-| The authentication token for the currently logged-in user.
+
+The token records the username associated with this token, which you can ask it for.
+
+By design, there is no way to access the token directly as a String. You can encode it for persistence, and you can add it to a header to a HttpBuilder for a request, but that's it.
+
+-}
+
+
 
 -- TYPES
 
 
-type alias Cred =
-    { username : Username
-    , token : String
-    }
+type Cred
+    = Cred Username String
+
+
+
+-- INFO
+
+
+username : Cred -> Username
+username (Cred val _) =
+    val
 
 
 
@@ -33,14 +65,14 @@ decoder =
 
 
 encodeToken : Cred -> Value
-encodeToken cred =
-    Encode.string cred.token
+encodeToken (Cred _ str) =
+    Encode.string str
 
 
 addHeader : Cred -> RequestBuilder a -> RequestBuilder a
-addHeader cred builder =
+addHeader (Cred _ str) builder =
     builder
-        |> withHeader "authorization" ("Token " ++ cred.token)
+        |> withHeader "authorization" ("Token " ++ str)
 
 
 addHeaderIfAvailable : Maybe Cred -> RequestBuilder a -> RequestBuilder a