Automatically ignore Rails' health-check

Adds the `Rails::HealthController#show` endpoint to the default
`ignore_actions` config by adding it to the Railtie loader defaults.

Suggested by a customer in:
https://app.intercom.com/a/inbox/yzor8gyw/inbox/shared/unassigned/conversation/16410700366724#part_id=comment-16410700366724-21909575460

Co-authored-by: Noemi <[email protected]>

.changesets/ignore-rails-healthcheck-by-default.md

@@ -0,0 +1,31 @@
+---
+bump: patch
+type: change
+---
+
+Ignore the Rails healthcheck endpoint (Rails::HealthController#show) by default for Rails apps.
+
+If the `ignore_actions` option is set in the `config/appsignal.yml` file, the default is overwritten.
+If the `APPSIGNAL_IGNORE_ACTIONS` environment variable is set, the default is overwritten.
+When using the `Appsignal.configure` helper, add more actions to the default like so:
+
+```ruby
+# config/appsignal.rb
+Appsignal.configure do |config|
+  # Add more actions to ignore
+  config.ignore_actions << "My action"
+end
+```
+
+To overwrite the default using the `Appsignal.configure` helper, do either of the following:
+
+```ruby
+# config/appsignal.rb
+Appsignal.configure do |config|
+  # Overwrite the default value, ignoring all actions ignored by default
+  config.ignore_actions = ["My action"]
+
+  # To only remove the healtcheck endpoint
+  config.ignore_actions.delete("Rails::HealthController#show")
+end
+```

lib/appsignal/integrations/railtie.rb

@@ -45,7 +45,8 @@ def self.load_default_config
           :root_path => Rails.root,
           :env => Rails.env,
           :name => Appsignal::Utils::RailsHelper.detected_rails_app_name,
-          :log_path => Rails.root.join("log")
+          :log_path => Rails.root.join("log"),
+          :ignore_actions => ["Rails::HealthController#show"]
         )
       end
 

spec/lib/appsignal/integrations/railtie_spec.rb

@@ -82,6 +82,8 @@ def initialize_railtie(event)
           expect(rails_defaults[:options][:name]).to eq("MyApp")
           expect(rails_defaults[:options][:log_path])
             .to eq(Pathname.new(File.join(rails_project_fixture_path, "log")))
+          expect(rails_defaults[:options][:ignore_actions])
+            .to eq(["Rails::HealthController#show"])
         end
 
         it "loads the app name from the project's appsignal.yml file" do