Deprecate BatchOver in favor of in_batches(use_ranges: true)

Starting from ActiveRecord 7.1, there's a built-in helper equivalent
to what BatchOver does, let's use it instead of maintaining our own
implementation forever.

We keep BatchOver for compatibility with ActiveRecord < 7.1.

lib/safe-pg-migrations/helpers/batch_over.rb

@@ -2,6 +2,25 @@
 
 module SafePgMigrations
   module Helpers
+    # This helper class allows to iterate over records in batches, in a similar
+    # way to ActiveRecord's `in_batches` method with the :use_ranges option,
+    # which was introduced in ActiveRecord 7.1.
+    #
+    # See:
+    #   - https://api.rubyonrails.org/classes/ActiveRecord/Batches.html#method-i-in_batches
+    #   - https://github.com/rails/rails/blob/v7.1.0/activerecord/CHANGELOG.md
+    #   - https://github.com/rails/rails/pull/45414
+    #   - https://github.com/rails/rails/commit/620f24782977b8e53e06cf0e2c905a591936e990
+    #
+    # If using ActiveRecord 7.1 or later, it's recommended to use the built-in
+    # method, e.g.
+    #
+    #   User.in_batches(of: 100, use_ranges: true).each { |batch| ... }
+    #
+    # Otherwise, this helper can be used as a fallback:
+    #
+    #   SafePgMigrations::Helpers::BatchOver.new(User, of: 100).each_batch { |batch| ... }
+    #
     class BatchOver
       def initialize(model, of: SafePgMigrations.config.backfill_batch_size)
         @model = model

lib/safe-pg-migrations/plugins/statement_insurer/add_column.rb

@@ -53,11 +53,19 @@ def backfill_column_default(table_name, column_name)
 
         Helpers::Logger.say_method_call(:backfill_column_default, table_name, column_name)
 
-        Helpers::BatchOver.new(model).each_batch do |batch|
+        batch_handler = lambda do |batch|
           batch.update_all("#{quoted_column_name} = DEFAULT")
 
           sleep SafePgMigrations.config.backfill_pause
         end
+
+        backfill_batch_size = SafePgMigrations.config.backfill_batch_size
+
+        if ActiveRecord.version >= Gem::Version.new('7.1')
+          model.in_batches(of: backfill_batch_size, use_ranges: true).each(&batch_handler)
+        else
+          Helpers::BatchOver.new(model, of: backfill_batch_size).each_batch(&batch_handler)
+        end
       end
     end
   end