Minor enhancements to Scala Play server generator (#2512)

* minor enhancements to openapi-generator

* update doc

* remove oudated doc

samples/server/petstore/scala-play-server/app/model/Order.scala

@@ -0,0 +1,33 @@
+package model
+
+import play.api.libs.json._
+import java.time.OffsetDateTime
+
+/**
+  * An order for a pets from the pet store
+  * @param status Order Status
+  */
+@javax.annotation.Generated(value = Array("org.openapitools.codegen.languages.ScalaPlayFrameworkServerCodegen"), date = "2019-03-26T16:21:58.590+08:00[Asia/Hong_Kong]")
+case class Order(
+  id: Option[Long],
+  petId: Option[Long],
+  quantity: Option[Int],
+  shipDate: Option[OffsetDateTime],
+  status: Option[Order.Status.Value],
+  complete: Option[Boolean]
+)
+
+object Order {
+  implicit lazy val orderJsonFormat: Format[Order] = Json.format[Order]
+
+  // noinspection TypeAnnotation
+  object Status extends Enumeration {
+    val Placed = Value("placed")
+    val Approved = Value("approved")
+    val Delivered = Value("delivered")
+
+    type Status = Value
+    implicit lazy val StatusJsonFormat: Format[Value] = Format(Reads.enumNameReads(this), Writes.enumNameWrites[this.type])
+  }
+}
+