feat: Add URL validation contract and error messages

[LyubomirT]

Description

Proposed Changes

Fixed issue #33 by adding the necessary error messages, classes, and methods to add the UrlValidationContract.

Review Checklist

• [x] I have read the Contributing.md
• [x] Tests have been added or updated to reflect the changes (if applicable).
• [x] An entry has been added to the changelog / My PR does not require a new changelog entry.
• [ ] The documentation in Portuguese has been updated or created, if necessary.
• [ ] If documentation was created, the update of the English file.
• [x] I have documented my changes in the code, adding docstrings and comments. Instructions
• [x] The code follows the project's style guidelines and coding standards.
• [x] All tests pass. Instructions
• [x] The Pull Request has been tested locally. Instructions
• [x] There are no merge conflicts.

Additional Comments (optional)

Related Issue

#33

Closes #33