Inherit email link addresses from hosting and proxy settings

backend/app/services/newsletters.py

@@ -32,7 +32,7 @@ def playback_url(runtime) -> str:
 def delivery_ready(public_url=None):
     config = store.settings()
     if not (public_url if public_url is not None else config['public_url']):
-        return False, 'Set the public Magent address for newsletter email links.'
+        return False, 'Set the application URL in Hosting & proxy for newsletter email links.'
     runtime = get_runtime_settings()
     if not runtime.jellyfin_base_url or not runtime.jellyfin_api_key:
         return False, 'Connect Jellyfin to collect new arrivals.'
@@ -150,7 +150,7 @@ async def preview(identity, revision):
     runtime = get_runtime_settings()
     config = store.settings()
     if not config['public_url'] or not playback_url(runtime):
-        raise NewsletterError('Set the public Magent and Jellyfin addresses before previewing.')
+        raise NewsletterError('Check the application URL in Hosting & proxy and the public playback URL in Jellyfin settings before previewing.')
     if row['content']['source'] != source_key(runtime.jellyfin_base_url) or row['content']['playback_url'] != playback_url(runtime):
         raise NewsletterError('The Jellyfin connection or public address changed. Create a fresh draft.')
     content = {**row['content'], 'subject': row['subject'], 'intro': row['intro']}