[#380] fix: Kotli MetaData experiments

(cherry picked from commit b5c2c88)

Author: MateuszNaKodach

kotlin/src/main/kotlin/org/axonframework/extensions/kotlin/serialization/AxonSerializers.kt

@@ -112,7 +112,7 @@ val `AxonSerializersModule` = SerializersModule {
         subclass(MultipleInstancesResponseTypeSerializer)
         subclass(ArrayResponseTypeSerializer)
     }
-    contextual(MetaData::class) { MetaDataSerializer }
+    contextual(MetaData::class) { MapSerializer(String.serializer(), String.serializer()) }
 }
 
 /**

kotlin/src/test/kotlin/org/axonframework/extensions/kotlin/serializer/AxonSerializersTest.kt

@@ -26,6 +26,7 @@ import org.axonframework.eventhandling.tokenstore.ConfigToken
 import org.axonframework.extensions.kotlin.messaging.responsetypes.ArrayResponseType
 import org.axonframework.extensions.kotlin.serialization.AxonSerializersModule
 import org.axonframework.extensions.kotlin.serialization.KotlinSerializer
+import org.axonframework.messaging.MetaData
 import org.axonframework.messaging.responsetypes.InstanceResponseType
 import org.axonframework.messaging.responsetypes.MultipleInstancesResponseType
 import org.axonframework.messaging.responsetypes.OptionalResponseType
@@ -35,6 +36,7 @@ import org.axonframework.serialization.SimpleSerializedObject
 import org.axonframework.serialization.SimpleSerializedType
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertInstanceOf
+import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.Test
 
 internal class AxonSerializersTest {
@@ -173,6 +175,26 @@ internal class AxonSerializersTest {
         assertEquals(responseType, serializer.deserializeResponseType(responseType.javaClass.name, json))
     }
 
+    @Test
+    fun metaDataSerialization() {
+        val metaData = MetaData.emptyInstance()
+        val json = """{}"""
+        val serialized = serializer.serialize(metaData, String::class.java).data
+
+        val serializedType = SimpleSerializedType(type, null)
+        val serializedToken = SimpleSerializedObject(json, String::class.java, serializedType)
+        return deserialize(serializedToken)
+        assertEquals(json, serialized)
+    }
+
+    @Test
+    fun metaDataSerialization2() {
+        val metaData = MetaData.with("key", "value")
+        val json = """{}"""
+        val serialized = serializer.serialize(metaData, String::class.java).data
+        assertEquals(json, serialized)
+    }
+
     private fun Serializer.deserializeTrackingToken(tokenType: String, json: String): TrackingToken =
         deserializeJson(tokenType, json)