Launch creator Onboarding with the Feature Flag [ To merge only on January 17 ] (#16090)

* feat: add the DUS script

* feat: enable the Feature Flag

lib/data_update_scripts/20220113085122_enable_creator_onboarding_feature_flag.rb

@@ -0,0 +1,8 @@
+module DataUpdateScripts
+  class EnableCreatorOnboardingFeatureFlag
+    def run
+      FeatureFlag.add(:creator_onboarding)
+      FeatureFlag.enable(:creator_onboarding)
+    end
+  end
+end

spec/lib/data_update_scripts/enable_creator_onboarding_feature_flag_spec.rb

@@ -0,0 +1,38 @@
+require "rails_helper"
+require Rails.root.join(
+  "lib/data_update_scripts/20220113085122_enable_creator_onboarding_feature_flag.rb",
+)
+
+describe DataUpdateScripts::EnableCreatorOnboardingFeatureFlag do
+  after do
+    FeatureFlag.remove(:creator_onboarding)
+  end
+
+  it "adds the :creator_onboarding flag" do
+    expect do
+      described_class.new.run
+    end.to change { FeatureFlag.exist?(:creator_onboarding) }.from(false).to(true)
+  end
+
+  it "enables the :creator_onboarding flag" do
+    expect do
+      described_class.new.run
+    end.to change { FeatureFlag.enabled?(:creator_onboarding) }.from(false).to(true)
+  end
+
+  it "works if the flag is already available" do
+    FeatureFlag.add(:creator_onboarding)
+
+    expect do
+      described_class.new.run
+    end.not_to change { FeatureFlag.exist?(:creator_onboarding) }
+  end
+
+  it "works if the flag is already enabled" do
+    FeatureFlag.enable(:creator_onboarding)
+
+    expect do
+      described_class.new.run
+    end.not_to change { FeatureFlag.enabled?(:creator_onboarding) }
+  end
+end