feat: LetterFeed icon for feed

backend/app/tests/test_routers.py

@@ -185,6 +185,9 @@ def test_get_newsletter_feed(client: TestClient):
     logo = root.find("atom:logo", ns)
     assert logo is not None
     assert logo.text == "http://localhost:8000/logo.png"
+    icon = root.find("atom:icon", ns)
+    assert icon is not None
+    assert icon.text == "http://localhost:8000/favicon.ico"
     entry_titles = [
         entry.find("atom:title", ns).text for entry in root.findall("atom:entry", ns)
     ]

backend/app/tests/test_services.py

@@ -41,6 +41,7 @@ def test_generate_feed(db_session: Session):
     assert f"<title>{newsletter.name}</title>" in feed_xml.decode()
     assert f"<id>urn:letterfeed:newsletter:{newsletter.id}</id>" in feed_xml.decode()
     assert "<logo>http://localhost:8000/logo.png</logo>" in feed_xml.decode()
+    assert "<icon>http://localhost:8000/favicon.ico</icon>" in feed_xml.decode()
     assert "<title>First Entry</title>" in feed_xml.decode()
     assert "<title>Second Entry</title>" in feed_xml.decode()
     assert (