Extract code for low-level work with order from Sort to OrderHelper

[vjik]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

[what-the-diff]

PR Summary

• Enhancements to Ordering Functions
  We've introduced a new helper class named OrderHelper. This class will take care of tasks related to converting and managing orders. It simplifies the process of working with orders, promotes code reuse, and centralizes this specific functionality.

• Refactoring Changes in Sort.php

  • The existing process that transformed order strings into arrays is now handled by a new method OrderHelper::stringToArray. This should help us manage this function more globally, increasing efficiency.

  • Similarly, the procedure for converting an order array back into a string now has been replaced with a call to OrderHelper::arrayToString. With this enhancement, code maintenance will be simplified because we are managing this operation from a single place.

• Test Coverage Improvements
  In order to verify the functionality of our new OrderHelper class, we've added OrderHelperTest.php. This ensures that the methods in 'OrderHelper' class function as expected and will alert us to any future disruptions to its functionality.