feature: support multiple application on single server

- kotlin idiom + doc
- fix #3645

Author: jknack

docs/asciidoc/routing.adoc

@@ -1364,11 +1364,11 @@ Done {love}!
 
 === Multiple routers
 
-This model let you `run` multiple applications independently on single server. Each application
+This model let you `run` multiple applications on single server instance. Each application
 works like a standalone application, they don't share any kind of services.
 
 .Multiple routers
-[source, java]
+[source, java,role="primary"]
 ----
 public class Foo extends Jooby {
   {
@@ -1393,6 +1393,17 @@ public class MultiApp {
 }
 ----
 
+.Kotlin
+[source, kotlin,role="secondary"]
+----
+
+import io.jooby.kt.Kooby.runApp
+
+fun main(args: Array<String>) {
+  runApp(args, ::Foo, ::Bar)
+}
+----
+
 You write your application as always and them you deploy them using the `runApp` method.
 
 [IMPORTANT]

modules/jooby-kotlin/src/main/kotlin/io/jooby/kt/Kooby.kt

@@ -21,11 +21,13 @@ import io.jooby.Route
 import io.jooby.RouteSet
 import io.jooby.Router
 import io.jooby.RouterOption
+import io.jooby.Server
 import io.jooby.ServerOptions
 import io.jooby.ServiceRegistry
 import io.jooby.Value
 import io.jooby.ValueNode
 import io.jooby.handler.Cors
+import java.util.function.Supplier
 import kotlin.reflect.KClass
 import kotlin.reflect.KProperty
 import kotlinx.coroutines.CoroutineStart
@@ -353,6 +355,27 @@ fun <T : Jooby> runApp(args: Array<String>, mode: ExecutionMode, provider: () ->
   Jooby.runApp(args, mode, provider)
 }
 
+fun <T : Jooby> runApp(args: Array<String>, vararg provider: () -> T) {
+  runApp(args, Server.loadServer(), ExecutionMode.DEFAULT, *provider)
+}
+
+fun <T : Jooby> runApp(args: Array<String>, mode: ExecutionMode, vararg provider: () -> T) {
+  runApp(args, Server.loadServer(), mode, *provider)
+}
+
+fun <T : Jooby> runApp(args: Array<String>, server: Server, vararg provider: () -> T) {
+  runApp(args, server, ExecutionMode.DEFAULT, *provider)
+}
+
+fun <T : Jooby> runApp(
+  args: Array<String>,
+  server: Server,
+  mode: ExecutionMode,
+  vararg provider: () -> T,
+) {
+  Jooby.runApp(args, server, mode, provider.map { Supplier<Jooby> { it.invoke() } }.toList())
+}
+
 internal fun configurePackage(value: Any) {
   val appname = value::class.java.name
   val start = appname.indexOf(".").let { if (it == -1) 0 else it + 1 }

tests/src/test/kotlin/KtMultiApp.kt

@@ -0,0 +1,18 @@
+/*
+ * Jooby https://jooby.io
+ * Apache License Version 2.0 https://jooby.io/LICENSE.txt
+ * Copyright 2014 Edgar Espina
+ */
+import examples.multiapp.BarApp
+import examples.multiapp.FooApp
+import io.jooby.ExecutionMode
+import io.jooby.kt.runApp
+import io.jooby.netty.NettyServer
+
+fun main(args: Array<String>) {
+  runApp(args, NettyServer(), ExecutionMode.DEFAULT, ::BarApp, ::FooApp)
+
+  runApp(args, NettyServer(), ::BarApp, ::FooApp)
+
+  runApp(args, ::BarApp, ::FooApp)
+}