s3 uploader: add new feature to force public attachment URIs to go through media proxy

lib/pleroma/uploaders/s3.ex

@@ -1,10 +1,13 @@
 defmodule Pleroma.Uploaders.S3 do
+  alias Pleroma.Web.MediaProxy
+
   @behaviour Pleroma.Uploaders.Uploader
 
   def put_file(name, uuid, path, content_type, _should_dedupe) do
     settings = Application.get_env(:pleroma, Pleroma.Uploaders.S3)
     bucket = Keyword.fetch!(settings, :bucket)
     public_endpoint = Keyword.fetch!(settings, :public_endpoint)
+    force_media_proxy = Keyword.fetch!(settings, :force_media_proxy)
 
     {:ok, file_data} = File.read(path)
 
@@ -19,7 +22,16 @@ defmodule Pleroma.Uploaders.S3 do
       ])
       |> ExAws.request()
 
-    {:ok, "#{public_endpoint}/#{bucket}/#{s3_name}"}
+    url_base = "#{public_endpoint}/#{bucket}/#{s3_name}"
+
+    public_url =
+      if force_media_proxy do
+        MediaProxy.url(url_base)
+      else
+        url_base
+      end
+
+    {:ok, public_url}
   end
 
   defp encode(name) do