Fix flatpak issues

Author: jobselko

CHANGES/+flatpak-index-cache.bugfix

@@ -0,0 +1 @@
+Fixed a serialization issue with the FlatpakIndex cache.

CHANGES/+flatpak-manifest-list-filter.bugfix

@@ -0,0 +1 @@
+Fixed OS and architecture filters being silently ignored when filtering manifest lists in the flatpak index.

pulp_container/app/registry_api.py

@@ -568,9 +568,9 @@ def recurse_through_manifest_lists(self, tag, manifest, oss, architectures, mani
         elif manifest.media_type in (models.MEDIA_TYPE.MANIFEST_LIST, models.MEDIA_TYPE.INDEX_OCI):
             mlms = manifest.listed_manifests.through.objects.filter(image_manifest__pk=manifest.pk)
             if oss:
-                mlms.filter(os__in=oss)
+                mlms = mlms.filter(os__in=oss)
             if architectures:
-                mlms.filter(architecture__in=architectures)
+                mlms = mlms.filter(architecture__in=architectures)
             for mlm in mlms:
                 self.recurse_through_manifest_lists(
                     tag, mlm.manifest_list, oss, architectures, manifests
@@ -676,7 +676,7 @@ def get(self, request):
                     continue
                 images.append(
                     {
-                        "Tags": tagged,
+                        "Tags": list(tagged),
                         "Digest": manifest.digest,
                         "MediaType": manifest.media_type,
                         "OS": os,