Download cutoff date for sources (#69)

* Added new uploaded_at column to media items

* Updated indexer to pull upload date

* Updates media item creation to update on conflict

* Added download cutoff date to sources

* Applies cutoff date logic to pending media logic

* Updated docs

.iex.exs

@@ -1,3 +1,4 @@
+import Ecto.Query, warn: false
 alias Pinchflat.Repo
 
 alias Pinchflat.Tasks.Task
@@ -35,6 +36,10 @@ defmodule IexHelpers do
     "https://www.youtube.com/watch?v=bR52O78ZIUw"
   end
 
+  def last_media_item do
+    Repo.one(from m in MediaItem, limit: 1)
+  end
+
   def details(type) do
     source =
       case type do