karafka-sidekiq-backend.gemspec in karafka-sidekiq-backend-1.4.7 vs karafka-sidekiq-backend.gemspec in karafka-sidekiq-backend-1.4.9

@@ -25,9 +25,15 @@
 
   spec.cert_chain    = %w[certs/mensfeld.pem]
   spec.files         = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(spec)/}) }
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = %w[lib]
+  spec.post_install_message = <<~MSG
+    WARN: Karafka Sidekiq Backend and Karafka 1.4 are no longer maintained.
+    Karafka 2.0 is multi-threaded and does not need an alternative backend.
+    We highly recommend updating to Karafka 2.0.
+    Visit this page for more details: https://karafka.io/docs/Upgrades-2.0
+  MSG
 
   spec.metadata = {
     'funding_uri' => 'https://karafka.io/#become-pro',
     'homepage_uri' => 'https://karafka.io',
     'changelog_uri' => 'https://github.com/karafka/sidekiq-backend/blob/master/CHANGELOG.md',