Refactor code

[martijn00]

Connection with issue(s)

Close #110

Solution description

Splits up the code into better testable and more maintainable code.

Screenshots or Videos

To Do

• Read contributing guide
• Check the original issue to confirm it is fully satisfied
• Add solution description to help guide reviewers
• Add unit test to verify new or fixed behaviour
• If apply, add documentation to code properties and package readme

[deandreamatias]

Thank you very much for working on it!
I'm very busy with my studies and work and couldn't continue with the other PR

[codecov]

Codecov Report

Attention: Patch coverage is 95.46828% with 45 lines in your changes missing coverage. Please review.

Project coverage is 95.00%. Comparing base (8f40bc6) to head (9cf707d).

Files	Patch %	Lines
lib/src/identity/username_validator.dart	72.97%	10 Missing ⚠️
lib/src/core/aggregate_validator.dart	81.81%	2 Missing ⚠️
lib/src/core/compose_validator.dart	75.00%	2 Missing ⚠️
lib/src/core/conditional_validator.dart	77.77%	2 Missing ⚠️
lib/src/core/default_value_validator.dart	75.00%	2 Missing ⚠️
lib/src/core/log_validator.dart	81.81%	2 Missing ⚠️
lib/src/core/not_equal_validator.dart	60.00%	2 Missing ⚠️
lib/src/core/or_validator.dart	75.00%	2 Missing ⚠️
lib/src/core/skip_when_validator.dart	77.77%	2 Missing ⚠️
lib/src/core/transform_validator.dart	77.77%	2 Missing ⚠️
... and 16 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #111      +/-   ##
==========================================
+ Coverage   93.31%   95.00%   +1.69%     
==========================================
  Files           5       92      +87     
  Lines         613     1002     +389     
==========================================
+ Hits          572      952     +380     
- Misses         41       50       +9     

Flag	Coverage Δ
unittests	95.00% <95.46%> (+1.69%)	⬆️

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[martijn00]

@deandreamatias this is now ready to go!

[martijn00]

@deandreamatias can you make the release?

[deandreamatias]

@martijn00 need more documentation about this changes.

1. Add breaking changes and how migrate on README
2. Add link to these section on changelog
3. Update the table of contents on readme
4. Update documentation on readme about how add new validator

If you can do this, I will appreciate