Fix deprecation: "using legacy connection handling is deprecated"

Author: Mattia Roccoberton

spec/dummy/config/application.rb

@@ -13,6 +13,9 @@ class Application < Rails::Application
     # Application configuration can go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded after loading
     # the framework and any gems in your application.
+
+    if (Rails::VERSION::MAJOR == 6 && Rails::VERSION::MINOR == 1) || Rails::VERSION::MAJOR >= 7
+      config.active_record.legacy_connection_handling = false
+    end
   end
 end
-