[kotlin][client] Use OffsetDateTime to represente date-time received by the server (#4835)

* [kotlin] add OffsetDateTime support

* [kotlin] serializer add missing import

* [kotlin] update pet projects and fix tests

* [kotlin] update docs

* [kotlin] update pet projects

* [kotlin] update date-time

* [kotlin] update pet project

* [kotlin] update windows script

samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/OffsetDateTimeAdapter.kt

@@ -0,0 +1,19 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.time.OffsetDateTime
+import java.time.format.DateTimeFormatter
+
+class OffsetDateTimeAdapter {
+    @ToJson
+    fun toJson(value: OffsetDateTime): String {
+        return DateTimeFormatter.ISO_OFFSET_DATE_TIME.format(value)
+    }
+
+    @FromJson
+    fun fromJson(value: String): OffsetDateTime {
+        return OffsetDateTime.parse(value, DateTimeFormatter.ISO_OFFSET_DATE_TIME)
+    }
+
+}

samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt

@@ -9,6 +9,7 @@ object Serializer {
     @JvmStatic
     val moshiBuilder: Moshi.Builder = Moshi.Builder()
         .add(Date::class.java, Rfc3339DateJsonAdapter().nullSafe())
+        .add(OffsetDateTimeAdapter())
         .add(LocalDateTimeAdapter())
         .add(LocalDateAdapter())
         .add(UUIDAdapter())

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

@@ -32,7 +32,7 @@ data class Order (
     @Json(name = "quantity")
     val quantity: kotlin.Int? = null,
     @Json(name = "shipDate")
-    val shipDate: java.time.LocalDateTime? = null,
+    val shipDate: java.time.OffsetDateTime? = null,
     /* Order Status */
     @Json(name = "status")
     val status: Order.Status? = null,

samples/client/petstore/kotlin/src/test/kotlin/org/openapitools/client/StoreApiTest.kt

@@ -6,7 +6,7 @@ import org.openapitools.client.apis.PetApi
 import org.openapitools.client.apis.StoreApi
 import org.openapitools.client.models.Order
 import org.openapitools.client.models.Pet
-import java.time.LocalDateTime.now
+import java.time.OffsetDateTime.now
 
 class StoreApiTest : ShouldSpec() {
     init {