Create Kotlin extension library for Javalin

There are lots of Kotlin guys that don’t like some parts of the syntax Javalin has. The extension library is just a bunch of different functions to allow more Kotlin-like syntax.

Example from #150 :

Current Kotlin code:

ctx.paramMap()["id"]?.let {
    ...
}

Extension function:

val Context.params: Map<String, String> = this.paramMap()

ctx.params["id"].let { }

The library could be supplied as a separate artifact (eg io.javalin.k-javalin or so) to not bother the Java users.

[ShikaSD]

I agree, though it is not limited to context params only. Will check if the extensions can improve the syntax more significantly, as I am not sure that Javalin will benefit from these (^^^) extensions a lot.

[tipsy]

Great, I’ve started thinking that keeping the library consistent across Java and Kotlin is a main goal of the project.