[feature] Dynamic error messages

[brayniverse]

I'm working on a new Strong Password validator that will help enforce the use of stronger passwords. The validator will offer various configurable checks such as:

• comparing the value against dictionary of common, easily guessable, passwords
• enforcing upper and lowercase letters
• etc

Because this validator is handling numerous business rules the error message must change based on which rule was broken. It would be great if there was a way to dynamically set or return the validation error message from the validate method or closure.

At the moment the only way to handle this scenario is to split each business rule into it's own validator, or return a generic "Password is too weak" error message.