Add feeds without subscribing

Adding feeds to the queue without subscribing is a long running
feature request. Doing this does not really make sense
on a distributed podcast app. However, to make these people happy,
subscribe to the feed internally anyway and just tell them that
it is not subscribed.

app/src/main/java/de/danoeh/antennapod/ui/screen/download/CompletedDownloadsFragment.java

@@ -297,7 +297,8 @@ private void loadItems() {
         disposable = Observable.fromCallable(() -> {
             SortOrder sortOrder = UserPreferences.getDownloadsSortedOrder();
             List<FeedItem> downloadedItems = DBReader.getEpisodes(0, Integer.MAX_VALUE,
-                        new FeedItemFilter(FeedItemFilter.DOWNLOADED), sortOrder);
+                    new FeedItemFilter(FeedItemFilter.DOWNLOADED, FeedItemFilter.INCLUDE_NOT_SUBSCRIBED),
+                    sortOrder);
 
             List<String> mediaUrls = new ArrayList<>();
             if (runningDownloads == null) {

app/src/main/java/de/danoeh/antennapod/ui/screen/feed/FeedItemlistFragment.java

@@ -483,6 +483,11 @@ private void refreshHeaderView() {
         } else {
             viewBinding.header.txtvInformation.setVisibility(View.GONE);
         }
+        boolean isSubscribed = feed.getState() == Feed.STATE_SUBSCRIBED;
+        viewBinding.header.butShowInfo.setVisibility(isSubscribed ? View.VISIBLE : View.GONE);
+        viewBinding.header.butFilter.setVisibility(isSubscribed ? View.VISIBLE : View.GONE);
+        viewBinding.header.butShowSettings.setVisibility(isSubscribed ? View.VISIBLE : View.GONE);
+        viewBinding.header.butSubscribe.setVisibility(isSubscribed ? View.GONE : View.VISIBLE);
     }
 
     private void setupHeaderView() {
@@ -494,6 +499,13 @@ private void setupHeaderView() {
         viewBinding.imgvBackground.setColorFilter(new LightingColorFilter(0xff666666, 0x000000));
         viewBinding.header.butShowInfo.setOnClickListener(v -> showFeedInfo());
         viewBinding.header.imgvCover.setOnClickListener(v -> showFeedInfo());
+        viewBinding.header.butSubscribe.setOnClickListener(view -> {
+            feed.getPreferences().setKeepUpdated(true);
+            DBWriter.setFeedPreferences(feed.getPreferences());
+            feed.setState(Feed.STATE_SUBSCRIBED);
+            DBWriter.setFeedState(feed);
+            FeedUpdateManager.getInstance().runOnceOrAsk(requireContext(), feed);
+        });
         viewBinding.header.butShowSettings.setOnClickListener(v -> {
             if (feed != null) {
                 FeedSettingsFragment fragment = FeedSettingsFragment.newInstance(feed);