Add id field for sending messages.

The idea is to use this field to dismiss messages only when
a sync response with their id arrives.

src/Main.elm

@@ -121,7 +121,7 @@ updateMarkdown m { roomId, text, markdown } =
         sendMessageCmd = sendMarkdownMessage m.apiUrl (Maybe.withDefault "" m.token) (m.transactionId + 1) roomId text markdown
         newModel =
             { m | transactionId = m.transactionId + 1
-            , sending = Dict.insert (m.transactionId + 1) (roomId, TextMessage text) m.sending
+            , sending = Dict.insert (m.transactionId + 1) (roomId, { body = TextMessage text, id = Nothing }) m.sending
             }
     in
         (newModel, Cmd.batch [ storeValueCmd, sendMessageCmd, requestScrollCmd ])

src/Scylla/Messages.elm

@@ -2,7 +2,12 @@ module Scylla.Messages exposing (..)
 import Scylla.Sync exposing (RoomEvent)
 import Scylla.Login exposing (Username)
 
-type SendingMessage = TextMessage String
+type SendingMessageBody = TextMessage String
+
+type alias SendingMessage =
+    { body : SendingMessageBody
+    , id : Maybe String
+    }
 
 type Message =
     Sending SendingMessage

src/Scylla/Views.elm

@@ -213,7 +213,7 @@ messageView m msg = case msg of
     Received re -> roomEventView m re
 
 sendingMessageView : Model -> SendingMessage -> Html Msg
-sendingMessageView m msg = case msg of
+sendingMessageView m msg = case msg.body of
     TextMessage t -> text t
 
 roomEventView : Model -> RoomEvent -> Maybe (Html Msg)