Update RequiredIf Validator to Accept UDF/Closure

[homestar9]

This change adds additional functionality to the RequiredIf validator. Now, you can pass a UDF/closure to the validator to dynamically evaluate whether the field is required or not. The UDF/closure should return true if the field is required and false if not.

Example:

// constraints
myField = {
    // myField is required if today is Monday.
    requiredIf = function( value, target, errorMetadata ) {
        return dayOfWeekAsString( dayOfWeek( now() ) ) == "Monday";
    }
}

[lmajano]

Looks great, make sure you document it kind sir!

[homestar9]

Docs updated here: ortus-docs/cbvalidation-docs#14