Add avatar URL to Webfinger when available

app/controllers/webfinger_controller.rb

@@ -33,6 +33,10 @@ class WebfingerController < WellKnownController
       links: []
     }
 
+    if @user.avatar.attached?
+      jrd[:links] += avatar_link
+    end
+
     if Setting.mastodon_enabled && @user.service_enabled?(:mastodon)
       # https://docs.joinmastodon.org/spec/webfinger/
       jrd[:aliases] += mastodon_aliases
@@ -47,6 +51,16 @@ class WebfingerController < WellKnownController
     jrd
   end
 
+  def avatar_link
+    [
+      {
+        rel: "http://webfinger.net/rel/avatar",
+        type: @user.avatar.content_type,
+        href: helpers.image_url_for(@user.avatar)
+      }
+    ]
+  end
+
   def mastodon_aliases
     [
       "#{Setting.mastodon_public_url}/@#{@user.cn}",