New improvements and test cases

[MattKeeley]

Merge Request Description

This merge request addresses several key improvements and enhancements:

1. Resolved False Negatives in Issue Spoofing not possible without SPF or DMARC record. #26:

   • Implemented recursive redirects to handle cases outlined in Issue #26.
   • Integrated the approach detailed in SPF Redirect Explained.

2. Program Modularization:

   • Refactored the process_domain function to be more modular, enabling its use as a library in other tools.

3. BIMI Record Resolver Cleanup:

   • Improved the clarity and efficiency of the BIMI record resolver.

4. Test Case Enhancements:

   • Developed clearer and more readable test cases, ensuring better coverage and easier maintenance.

5. New Logic for DMARC and SPF Records:

   • Added logic to handle DMARC and SPF records with broken syntax, addressing potential spoofing vulnerabilities.

6. Syntax Validation Class:

   • Introduced a SyntaxValidator class to ensure SPF and DMARC records conform to RFC syntax requirements before evaluation.

7. Threading Support:

   • Added a -t option for threading, allowing for more efficient processing of multiple records.