Extract render svg as a real renderer

app/controllers/accounts/join_codes_controller.rb

@@ -1,16 +1,10 @@
 class Accounts::JoinCodesController < ApplicationController
   def show
-    render_svg RQRCode::QRCode.new(join_url(Current.account.join_code)).as_svg(viewbox: true, fill: :white, color: :black)
+    render svg: RQRCode::QRCode.new(join_url(Current.account.join_code)).as_svg(viewbox: true, fill: :white, color: :black)
   end
 
   def update
     Current.account.reset_join_code
     redirect_to account_users_path
   end
-
-  private
-    # FIXME: Upstream to Rails as render svg:
-    def render_svg(svg)
-      render content_type: Mime[:svg], body: svg
-    end
 end

config/initializers/action_controller_svg_renderer.rb

@@ -0,0 +1,7 @@
+# FIXME: Upstream to Rails
+Rails.application.config.after_initialize do
+  ActionController.add_renderer :svg do |svg, options|
+    self.content_type = Mime[:svg] if media_type.nil?
+    svg
+  end
+end