Add part3

advanced/part3/src/Username.elm

@@ -0,0 +1,47 @@
+module Username exposing (Username, decoder, encode, toHtml, toString, urlParser)
+
+import Html exposing (Html)
+import Json.Decode as Decode exposing (Decoder)
+import Json.Encode as Encode exposing (Value)
+import Url.Parser
+
+
+
+-- TYPES
+
+
+type Username
+    = Username String
+
+
+
+-- CREATE
+
+
+decoder : Decoder Username
+decoder =
+    Decode.map Username Decode.string
+
+
+
+-- TRANSFORM
+
+
+encode : Username -> Value
+encode (Username username) =
+    Encode.string username
+
+
+toString : Username -> String
+toString (Username username) =
+    username
+
+
+urlParser : Url.Parser.Parser (Username -> a) a
+urlParser =
+    Url.Parser.custom "USERNAME" (\str -> Just (Username str))
+
+
+toHtml : Username -> Html msg
+toHtml (Username username) =
+    Html.text username