Refactor Spain country handler to support Natural Persons without DNI or NIE and Non-Natural Persons TIN formats

[alphp]

Rebased changes of #36

[what-the-diff]

PR Summary

• New File for Spain's Tax Identification Numbers
  A new document has been added, providing information about tax identification numbers (TIN) in Spain. This can serve a useful reference for understanding tax-related rules and regulations in Spain.

• Updating Spain's Tax Identification Algorithm
  The code files relating to Spain's TIN validation and implementation have been updated:

  • Constants related to the validation of TINs have been updated in the SpainSpec.php file.
  • A method has been updated in the CountryHandler.php file to ignore case sensitivity during pattern matching, effectively enhancing the system's robustness in handling user inputs.
  • In the Spain.php file, several methods have been revamped. The changes include updates to the values of the NIE constant, incorporation of the checksum handling into various methods for improved functional accuracy and updates in validation rules.

These changes provide a more accurate validation process for Spain's TINs, improving the robustness and reliability of the system overall.

[drupol]

Sad you opened a new PR :( but OK I'll give my final thoughts tomorrow.

[alphp]

I can't express my anger at having to do it like this after so much work.
But this week has been very complicated both personally and professionally: I can't take it anymore.

[drupol]

I can take care of it if you want, so we don't loose the history? Are you OK if I do it myself?

[alphp]

That would be great.
Thank you so much for all your patience with me.

[drupol]

That would be great. Thank you so much for all your patience with me.

No problem, can you check if I have the right to push to your repo? add me as collaborator and I'll fix the mess.

ERROR: Permission to fawno/tin.git denied to drupol.