Move TrackTrueClientIp middleware into saas engine (#2677)

The True-Client-IP header is set by Cloudflare and is only trustworthy
when behind a Cloudflare proxy. In non-Cloudflare deployments, this
header is attacker-controlled and can be used to spoof IP addresses.

Moving the middleware into the saas engine ensures it only loads for our
Cloudflare-fronted production deployment, not for self-hosted OSS
instances.

GHSA-cpch-9qg2-x8fq

saas/lib/fizzy/saas/engine.rb

@@ -1,4 +1,5 @@
 require_relative "transaction_pinning"
+require_relative "true_client_ip"
 require_relative "signup"
 require_relative "authorization"
 require_relative "gvl_instrumentation"
@@ -61,6 +62,10 @@ module Fizzy
         app.config.middleware.insert_after(ActiveRecord::Middleware::DatabaseSelector, TransactionPinning::Middleware)
       end
 
+      initializer "fizzy_saas.true_client_ip" do |app|
+        app.config.middleware.insert_before ActionDispatch::RemoteIp, TrackTrueClientIp
+      end
+
       initializer "fizzy_saas.gvl_instrumentation" do |app|
         app.config.middleware.insert_before(Rack::Runtime, GvlInstrumentation)
       end

saas/lib/fizzy/saas/true_client_ip.rb

@@ -20,5 +20,3 @@ class TrackTrueClientIp
     @app.call(env)
   end
 end
-
-Rails.application.config.middleware.insert_before ActionDispatch::RemoteIp, TrackTrueClientIp