Move global method to Feature class

It is surprising that this method, feature_flags_available is available
globally. Also it is surprising that this method is available only if
Gitlab.com? or in development. So we fix this by moving the method
definition to be a class method in Feature

config/initializers/active_record_transaction_observer.rb

@@ -2,17 +2,8 @@
 
 return unless Gitlab.com? || Gitlab.dev_or_test_env?
 
-def feature_flags_available?
-  # When the DBMS is not available, an exception (e.g. PG::ConnectionBad) is raised
-  active_db_connection = ActiveRecord::Base.connection.active? rescue false
-
-  active_db_connection && Feature::FlipperFeature.table_exists?
-rescue ActiveRecord::NoDatabaseError
-  false
-end
-
 Gitlab::Application.configure do
-  if feature_flags_available? && ::Feature.enabled?(:active_record_transactions_tracking, type: :ops, default_enabled: :yaml)
+  if Feature.feature_flags_available? && ::Feature.enabled?(:active_record_transactions_tracking, type: :ops, default_enabled: :yaml)
     Gitlab::Database::Transaction::Observer.register!
   end
 end

lib/feature.rb

@@ -29,6 +29,15 @@ class Feature
   class << self
     delegate :group, to: :flipper
 
+    def feature_flags_available?
+      # When the DBMS is not available, an exception (e.g. PG::ConnectionBad) is raised
+      active_db_connection = ActiveRecord::Base.connection.active? rescue false
+
+      active_db_connection && Feature::FlipperFeature.table_exists?
+    rescue ActiveRecord::NoDatabaseError
+      false
+    end
+
     def all
       flipper.features.to_a
     end