WIP. Implement oembed route and handle both json/xml for "Note" type activity

lib/pleroma/formatter.ex

@@ -163,4 +163,20 @@ defmodule Pleroma.Formatter do
       String.replace(result_text, uuid, replacement)
     end)
   end
+
+  def truncate(text, opts \\ []) do
+    max_length  = opts[:max_length] || 200
+    omission    = opts[:omission] || "..."
+
+    cond do
+      not String.valid?(text) ->
+        text
+      String.length(text) < max_length ->
+        text
+      true ->
+        length_with_omission = max_length - String.length(omission)
+
+        "#{String.slice(text, 0, length_with_omission)}#{omission}"
+    end
+  end
 end