[BUG][Kotlin Client] API using case other than camelCase not generated properly (#2391)

* Add Json import for all data classes

* Add `@Json` annotation for data class required variables

* Add `@json` annotation for data class optional variables

* Update samples code (petstore, strings, threetenbp)

* Fix annotation to match Kotlin coding style

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

@@ -12,6 +12,7 @@
 package org.openapitools.client.models
 
 
+import com.squareup.moshi.Json
 /**
  * Describes the result of uploading an image resource
  * @param code 
@@ -19,8 +20,11 @@ package org.openapitools.client.models
  * @param message 
  */
 data class ApiResponse (
+    @Json(name = "code")
     val code: kotlin.Int? = null,
+    @Json(name = "type")
     val type: kotlin.String? = null,
+    @Json(name = "message")
     val message: kotlin.String? = null
 ) {
 

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

@@ -12,13 +12,16 @@
 package org.openapitools.client.models
 
 
+import com.squareup.moshi.Json
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
 data class Category (
+    @Json(name = "id")
     val id: kotlin.Long? = null,
+    @Json(name = "name")
     val name: kotlin.String? = null
 ) {
 

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

@@ -23,12 +23,18 @@ import com.squareup.moshi.Json
  * @param complete 
  */
 data class Order (
+    @Json(name = "id")
     val id: kotlin.Long? = null,
+    @Json(name = "petId")
     val petId: kotlin.Long? = null,
+    @Json(name = "quantity")
     val quantity: kotlin.Int? = null,
+    @Json(name = "shipDate")
     val shipDate: java.time.LocalDateTime? = null,
     /* Order Status */
+    @Json(name = "status")
     val status: Order.Status? = null,
+    @Json(name = "complete")
     val complete: kotlin.Boolean? = null
 ) {
 
@@ -38,11 +44,14 @@ data class Order (
     */
     enum class Status(val value: kotlin.String){
     
-        @Json(name = "placed") placed("placed"),
+        @Json(name = "placed")
+        placed("placed"),
     
-        @Json(name = "approved") approved("approved"),
+        @Json(name = "approved")
+        approved("approved"),
     
-        @Json(name = "delivered") delivered("delivered");
+        @Json(name = "delivered")
+        delivered("delivered");
     
     }
 

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

@@ -25,12 +25,18 @@ import com.squareup.moshi.Json
  * @param status pet status in the store
  */
 data class Pet (
+    @Json(name = "name")
     val name: kotlin.String,
+    @Json(name = "photoUrls")
     val photoUrls: kotlin.Array<kotlin.String>,
+    @Json(name = "id")
     val id: kotlin.Long? = null,
+    @Json(name = "category")
     val category: Category? = null,
+    @Json(name = "tags")
     val tags: kotlin.Array<Tag>? = null,
     /* pet status in the store */
+    @Json(name = "status")
     val status: Pet.Status? = null
 ) {
 
@@ -40,11 +46,14 @@ data class Pet (
     */
     enum class Status(val value: kotlin.String){
     
-        @Json(name = "available") available("available"),
+        @Json(name = "available")
+        available("available"),
     
-        @Json(name = "pending") pending("pending"),
+        @Json(name = "pending")
+        pending("pending"),
     
-        @Json(name = "sold") sold("sold");
+        @Json(name = "sold")
+        sold("sold");
     
     }
 

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

@@ -12,13 +12,16 @@
 package org.openapitools.client.models
 
 
+import com.squareup.moshi.Json
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
 data class Tag (
+    @Json(name = "id")
     val id: kotlin.Long? = null,
+    @Json(name = "name")
     val name: kotlin.String? = null
 ) {
 

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

@@ -12,6 +12,7 @@
 package org.openapitools.client.models
 
 
+import com.squareup.moshi.Json
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -24,14 +25,22 @@ package org.openapitools.client.models
  * @param userStatus User Status
  */
 data class User (
+    @Json(name = "id")
     val id: kotlin.Long? = null,
+    @Json(name = "username")
     val username: kotlin.String? = null,
+    @Json(name = "firstName")
     val firstName: kotlin.String? = null,
+    @Json(name = "lastName")
     val lastName: kotlin.String? = null,
+    @Json(name = "email")
     val email: kotlin.String? = null,
+    @Json(name = "password")
     val password: kotlin.String? = null,
+    @Json(name = "phone")
     val phone: kotlin.String? = null,
     /* User Status */
+    @Json(name = "userStatus")
     val userStatus: kotlin.Int? = null
 ) {