[Scala] Properly handle csv collectionFormat (#6540)

* Add support for lists of path parameters (eg instances), and default params for optional case classes

* Update Petstore sample

* Revert defaulting of case class fields to None

* Update Petstore sample

Author: gmarz

modules/swagger-codegen/src/main/resources/scala/apiInvoker.mustache

@@ -53,6 +53,9 @@ class ApiInvoker(val mapper: ObjectMapper = ScalaJsonUtil.getJsonMapper,
   def escape(value: String): String = {
     URLEncoder.encode(value, "utf-8").replaceAll("\\+", "%20")
   }
+  def escape(values: List[String]): String = {
+     values.map(escape).mkString(",")
+  }
 
   def escape(value: Long): String = value.toString
   def escape(value: Double): String = value.toString

samples/client/petstore-security-test/scala/src/main/scala/io/swagger/client/ApiInvoker.scala

@@ -63,6 +63,9 @@ class ApiInvoker(val mapper: ObjectMapper = ScalaJsonUtil.getJsonMapper,
   def escape(value: String): String = {
     URLEncoder.encode(value, "utf-8").replaceAll("\\+", "%20")
   }
+  def escape(values: List[String]): String = {
+     values.map(escape).mkString(",")
+  }
 
   def escape(value: Long): String = value.toString
 

samples/client/petstore/scala/src/main/scala/io/swagger/client/ApiInvoker.scala

@@ -64,6 +64,9 @@ class ApiInvoker(val mapper: ObjectMapper = ScalaJsonUtil.getJsonMapper,
   def escape(value: String): String = {
     URLEncoder.encode(value, "utf-8").replaceAll("\\+", "%20")
   }
+  def escape(values: List[String]): String = {
+     values.map(escape).mkString(",")
+  }
 
   def escape(value: Long): String = value.toString
   def escape(value: Double): String = value.toString