Added OPML Endpoint for podcast rss feeds (#512)

* Added OPML Endpoint for podcast rss feeds

* changed opml route and added controller test for opml endpoint

* add copy opml feed button

* add copy opml feed button - correct url

* fix html indenting

* add indentation to opml

Co-authored-by: Kieran <kieran.eglin@gmail.com>

* use convention for unused controller params

Co-authored-by: Kieran <kieran.eglin@gmail.com>

* add test for opml_sources helper function

* change opml endpoint to be more inline with the other routes

---------

Co-authored-by: robs <git@robs.social>
Co-authored-by: Kieran <kieran.eglin@gmail.com>

test/pinchflat_web/controllers/podcast_controller_test.exs

@@ -4,6 +4,20 @@ defmodule PinchflatWeb.PodcastControllerTest do
   import Pinchflat.MediaFixtures
   import Pinchflat.SourcesFixtures
 
+  describe "opml_feed" do
+    test "renders the XML document", %{conn: conn} do
+      source = source_fixture()
+
+      conn = get(conn, ~p"/sources/opml" <> ".xml")
+
+      assert conn.status == 200
+      assert {"content-type", "application/opml+xml; charset=utf-8"} in conn.resp_headers
+      assert {"content-disposition", "inline"} in conn.resp_headers
+      assert conn.resp_body =~ ~s"http://www.example.com/sources/#{source.uuid}/feed.xml"
+      assert conn.resp_body =~ "text=\"Cool and good internal name!\""
+    end
+  end
+
   describe "rss_feed" do
     test "renders the XML document", %{conn: conn} do
       source = source_fixture()