[kotlin-client][kotlin-server] Feature/kotlin data class serial version uid (#4021)

* feat: add companion object to data classes if the implement the interface java.io.Serializable

* style: format template file

* style: adapt to project's original code style

* fix: add missing imports

* style: reverted mustache template to original styling

* test: generate additional samples for kotlin-springboot-reactive and kotlin-springboot

* docs: name full qualified classname of interface java.io.Serializable to prevent confusion with kotlinx.serialization

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/ApiResponse.kt

@@ -31,4 +31,9 @@ data class ApiResponse (
 ) 
 : Serializable 
 
+{
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+}
 

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/Category.kt

@@ -28,4 +28,9 @@ data class Category (
 ) 
 : Serializable 
 
+{
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+}
 

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/Order.kt

@@ -42,6 +42,10 @@ data class Order (
 : Serializable 
 
 {
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+
 
     /**
     * Order Status

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/Pet.kt

@@ -44,6 +44,10 @@ data class Pet (
 : Serializable 
 
 {
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+
 
     /**
     * pet status in the store

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/Tag.kt

@@ -28,4 +28,9 @@ data class Tag (
 ) 
 : Serializable 
 
+{
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+}
 

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/models/User.kt

@@ -47,4 +47,9 @@ data class User (
 ) 
 : Serializable 
 
+{
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+}