append_to_connected_to_stack

# File activerecord/lib/active_record/connection_handling.rb, line 368
      def append_to_connected_to_stack(entry)
        if shard_swapping_prohibited? && entry[:shard].present?
          raise ArgumentError, "cannot swap `shard` while shard swapping is prohibited."
        end

        connected_to_stack << entry
      end