This PR contains the work done to implement the `ValidateInputUseCase` use case and the `InputValidationRule` protocol, that is essential to define custom validation rules for inputs. In addition, the `NotEmptyValidationRule` and `NotNilValidationRule` rules have also been implemented.
Reviewed-on: #4
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>
