Implement updated UI for displaying the signing status of a tag, now that we support multiple delegations

The icon now represents the status of the multiple delegations, and we show each delegation in the "Expanded" view.

endpoints/api/signing.py

@@ -27,9 +27,4 @@ class RepositorySignatures(RepositoryParamResource):
     if repo is None or not repo.trust_enabled:
       raise NotFound()
 
-    tag_data, expiration = tuf_metadata_api.get_default_tags_with_expiration(namespace, repository)
-    return {
-      'tags': tag_data,
-      'expiration': expiration
-    }
-
+    return {'delegations': tuf_metadata_api.get_all_tags_with_expiration(namespace, repository)}