Javalin 4: Construct validator from typed object

Describe the feature In Javalin 3 Validator could be constructed from typed object:

open class Validator<T>(val value: T?, val messagePrefix: String = "Value", val key: String = "Parameter") {
...

In Javalin 4 the only way to construct Validator is to convert from string to typed object.

Additional context This makes harder to convert code from Javalin 3 to Javalin 4, when Javalin’s Validator used for validation of existing typed objects. To migrate such code, I’d not like to convert back and forth to/from string to get object into Validator, especially if object contains input stream with potentially long data.

p.s. I can try to submit patch for this.

[IvanPizhenko]

Good question. But I think I have an idea. Will make another PR.

[IvanPizhenko]

@tipsy Please look at #1396