Put the <link>s for PGP keys into the page header instead of the h-card itself, since it's invalid HTML to have <link> in the body

src/Widget/Card.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE TemplateHaskell #-}
 module Widget.Card ( hCard ) where
 
@@ -31,4 +32,8 @@ hCard (Entity userId user) = do
         E.orderBy [E.asc $ site ^. SiteName]
         return (site, profile)
     pgpKeys <- handlerToWidget . runDB $ map entityVal <$> selectList [PgpKeyUserId ==. userId] []
+    toWidgetHead [hamlet|
+        $forall key <- pgpKeys
+            <link rel="pgpkey" type="application/pgp-keys" href=@{routeFromPgp key}>
+    |]
     $(widgetFile "mf2/h-card")