Add :eph field to %TranslationUnit{} and remove :sibling_with

Using :eph from now on to store ephemeral data like :sibling_with. Additionally
added cleaning up :eph before saving to db. And renamed InternalTree.Basic
to InternalTree.RawInternalBasic to make clear that it contains function
for an intermediary tree structure.

lib/outlook_web/live/article_live/new.ex

@@ -4,7 +4,7 @@ defmodule OutlookWeb.ArticleLive.New do
   import OutlookWeb.ArticleLive.NewComponents
 
   alias OutlookWeb.ArticleLive.FormComponent
-  alias Outlook.{Articles,Authors,HtmlPreparations}
+  alias Outlook.{Articles,Authors,HtmlPreparations,InternalTree}
   alias Articles.{Article,RawHtmlInput}
 
   require Logger
@@ -52,6 +52,9 @@ defmodule OutlookWeb.ArticleLive.New do
 
   @impl true
   def handle_event("approve_raw_internaltree", _, socket) do
+      socket = socket
+      |> assign(:raw_internal_tree,
+          InternalTree.partition_text(socket.assigns.raw_internal_tree))
     {:noreply, socket |> assign(:step, :review_translation_units)}
   end