[Kotlin][Client] Request date converter (#4750)

* Added new cli option to define the request date converter

* Fixed a few build errors

* Update api.mustache

* Fixed api mustache

* Removed unused import

* Fixing mustache templates

* Tweaking mustache templates

* Added sample and new bat file

TODO create new openapi 2.0 source file to simulate the datestring via schema.

* Tweaking mustache templates

* Updated templates and samples

* Fixed build error

* Updated samples

* Fixed path

samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -170,4 +170,8 @@ open class ApiClient(val baseUrl: String) {
             )
         }
     }
+
+    protected inline fun <reified T: Any> parseDateToQueryString(value : T): String {
+        return value.toString()
+    }
 }