[Enhancement] Allow redownloading of files for existing media items (#239)

* Added ability to specify overwrite behaviour when downloading media

* Added helper for redownloading media items

* renamed media redownload worker to disambiguate it from similarly named methods

* Added new redownload option to source actions dropdown

* Refactored MediaQuery to use a __using__ macro

* docs

lib/pinchflat_web/controllers/sources/source_controller.ex

@@ -104,7 +104,7 @@ defmodule PinchflatWeb.Sources.SourceController do
     |> redirect(to: ~p"/sources")
   end
 
-  def force_download(conn, %{"source_id" => id}) do
+  def force_download_pending(conn, %{"source_id" => id}) do
     wrap_forced_action(
       conn,
       id,
@@ -113,6 +113,15 @@ defmodule PinchflatWeb.Sources.SourceController do
     )
   end
 
+  def force_redownload(conn, %{"source_id" => id}) do
+    wrap_forced_action(
+      conn,
+      id,
+      "Forcing re-download of downloaded media items.",
+      &DownloadingHelpers.kickoff_redownload_for_existing_media/1
+    )
+  end
+
   def force_index(conn, %{"source_id" => id}) do
     wrap_forced_action(
       conn,