Add ValueClassBoxConverter

from https://github.com/ProjectMapK/jackson-module-kogera/blob/dcc5e9cc2863a8261035692da86ed1d659520512/src/main/kotlin/com/fasterxml/jackson/module/kotlin/ser/ValueClassBoxConverter.kt

Author: k163377

src/main/kotlin/com/fasterxml/jackson/module/kotlin/Converters.kt

@@ -0,0 +1,21 @@
+package com.fasterxml.jackson.module.kotlin
+
+import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
+import com.fasterxml.jackson.databind.util.StdConverter
+import kotlin.reflect.KClass
+
+// S is nullable because value corresponds to a nullable value class
+// @see KotlinNamesAnnotationIntrospector.findNullSerializer
+internal class ValueClassBoxConverter<S : Any?, D : Any>(
+    unboxedClass: Class<S>,
+    valueClass: KClass<D>
+) : StdConverter<S, D>() {
+    private val boxMethod = valueClass.java.getDeclaredMethod("box-impl", unboxedClass).apply {
+        if (!this.isAccessible) this.isAccessible = true
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    override fun convert(value: S): D = boxMethod.invoke(null, value) as D
+
+    val delegatingSerializer: StdDelegatingSerializer by lazy { StdDelegatingSerializer(this) }
+}