System Overhaul: Transition to Modules and introduction of unittests

[Nephim]

I've implemented several key improvements inspired by PR #6:

• Stateless IP Checking: The system now dynamically retrieves the current IP registered for a domain, eliminating the need to store it in a file.
• Modular Architecture: All logic has been moved into a dedicated modules folder, ensuring a clear separation of concerns.
• Runtime Configurability: Hard-coded values have been augmented with runtime arguments (-u for username and -p for password), which can also be set via environment variables.
• Enhanced Logging & Safety: I've added colored logging for improved readability, and by default, the system now requires confirmation before making any changes to the DNS record which can be disabled with an option or env variable.
• Unit testing: Unit tests have been integrated to hopefully boost overall stability and reliability.

I made these changes to enable easier use with for example Docker by removing stored state and hardcoded sensitive information. I'd love to hear your feedback on these enhancements!

[lgc-4]

Hi, thank you for your work! Unfortunately I no longer manage my Domains using one.com so I can't really test these changes. Maybe keep them as a fork, I'll update the readme to link to it.