[Enhancement] Delete media after "x" days (#160)

* [Enhancement] Adds ability to stop media from re-downloading (#159)

* Added column

* Added methods for ignoring media items from future download

* Added new deletion options to controller and UI

* Added controller actions and UI for editing a media item

* Added column to sources

* Added retention period to form

* [WIP] getting retention methods in place

* Hooked up retention worker

* Added column and UI to prevent automatic deletion

* Docs

* Removed unused backfill worker

* Added edit links to media item tabs on source view

* Clarified form wording

* Form wording (again)

config/config.exs

@@ -46,7 +46,13 @@ config :pinchflat, Oban,
   engine: Oban.Engines.Lite,
   repo: Pinchflat.Repo,
   # Keep old jobs for 30 days for display in the UI
-  plugins: [{Oban.Plugins.Pruner, max_age: 30 * 24 * 60 * 60}],
+  plugins: [
+    {Oban.Plugins.Pruner, max_age: 30 * 24 * 60 * 60},
+    {Oban.Plugins.Cron,
+     crontab: [
+       {"@daily", Pinchflat.Downloading.MediaRetentionWorker}
+     ]}
+  ],
   # TODO: consider making this an env var or something?
   queues: [
     default: 10,