Merge commit '98237207e67697abffc6b141f2388e3d8c925260' into glitch-soc/merge-upstream

Conflicts:
- `app/helpers/application_helper.rb`:
  Upstream refactored some helpers and moved them in another file.
  Not a real conflict, but glitch-soc had adjacent glitch-only definitions.
  Kept glitch-soc definitions where they are and moved upstream ones
  as upstream did.

app/serializers/rest/instance_serializer.rb

@@ -7,10 +7,11 @@ class REST::InstanceSerializer < ActiveModel::Serializer
     has_one :account, serializer: REST::AccountSerializer
   end
 
+  include InstanceHelper
   include RoutingHelper
 
   attributes :domain, :title, :version, :source_url, :description,
-             :usage, :thumbnail, :languages, :configuration,
+             :usage, :thumbnail, :icon, :languages, :configuration,
              :registrations, :api_versions
 
   has_one :contact, serializer: ContactSerializer
@@ -33,6 +34,18 @@ class REST::InstanceSerializer < ActiveModel::Serializer
     end
   end
 
+  def icon
+    SiteUpload::ANDROID_ICON_SIZES.map do |size|
+      src = app_icon_path(size.to_i)
+      src = URI.join(root_url, src).to_s if src.present?
+
+      {
+        src: src || frontend_asset_url("icons/android-chrome-#{size}x#{size}.png"),
+        size: "#{size}x#{size}",
+      }
+    end
+  end
+
   def usage
     {
       users: {