add tests and make several replacements/improvements

startup/plugin/src/commonMain/kotlin/ServerPlugin.kt

@@ -1,34 +1,13 @@
 package dev.inmo.micro_utils.startup.plugin
 
-import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializable
-import kotlinx.serialization.builtins.serializer
-import kotlinx.serialization.descriptors.SerialDescriptor
-import kotlinx.serialization.encoding.Decoder
-import kotlinx.serialization.encoding.Encoder
 import kotlinx.serialization.json.JsonObject
 import org.koin.core.Koin
 import org.koin.core.module.Module
 
-@Serializable(ServerPlugin.Companion::class)
+@Serializable(ServerPluginSerializer::class)
 interface ServerPlugin {
     fun Module.setupDI(config: JsonObject) {}
 
     suspend fun startPlugin(koin: Koin) {}
-
-    companion object : KSerializer<ServerPlugin> {
-        override val descriptor: SerialDescriptor
-            get() = String.serializer().descriptor
-
-        override fun deserialize(decoder: Decoder): ServerPlugin {
-            val kclass = Class.forName(decoder.decodeString()).kotlin
-            return (kclass.objectInstance ?: kclass.constructors.first { it.parameters.isEmpty() }.call()) as ServerPlugin
-        }
-
-        override fun serialize(encoder: Encoder, value: ServerPlugin) {
-            encoder.encodeString(
-                value::class.java.canonicalName
-            )
-        }
-    }
 }

startup/plugin/src/commonMain/kotlin/ServerPluginSerializer.kt

@@ -0,0 +1,5 @@
+package dev.inmo.micro_utils.startup.plugin
+
+import kotlinx.serialization.KSerializer
+
+expect object ServerPluginSerializer : KSerializer<ServerPlugin>

startup/plugin/src/jvmMain/kotlin/ServerPluginSerializer.kt

@@ -0,0 +1,23 @@
+package dev.inmo.micro_utils.startup.plugin
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.builtins.serializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+actual object ServerPluginSerializer : KSerializer<ServerPlugin> {
+    override val descriptor: SerialDescriptor
+    get() = String.serializer().descriptor
+
+    override fun deserialize(decoder: Decoder): ServerPlugin {
+        val kclass = Class.forName(decoder.decodeString()).kotlin
+        return (kclass.objectInstance ?: kclass.constructors.first { it.parameters.isEmpty() }.call()) as ServerPlugin
+    }
+
+    override fun serialize(encoder: Encoder, value: ServerPlugin) {
+        encoder.encodeString(
+            value::class.java.canonicalName
+        )
+    }
+}