[kotlin] Make API classes open (non-final) unless nonPublicApi is used (#22461)

* [kotlin] Make API classes open (non-final) unless nonPublicApi is used

By making those classes open, AspectJ can be used to enhance their
behavior.

I'm not changing kotlin-multiplatform templates, where 'open' was
already present before my changes.

Closes #22271

* Fail Kotlin sample compilation if API classes stop to be public

Serves as a 'regression test'.

Author: pkubowicz

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/api.mustache

@@ -48,7 +48,7 @@ import {{packageName}}.infrastructure.Success
 import {{packageName}}.infrastructure.toMultiValue
 
 {{#operations}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}class {{classname}}(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}open {{/nonPublicApi}}class {{classname}}(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}companion object {
         @JvmStatic
         {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val defaultBasePath: String by lazy {

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-spring-restclient/api.mustache

@@ -20,7 +20,7 @@ import org.springframework.http.MediaType
 import {{packageName}}.infrastructure.*
 
 {{#operations}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}class {{classname}}(client: RestClient) : ApiClient(client) {
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}open {{/nonPublicApi}}class {{classname}}(client: RestClient) : ApiClient(client) {
 
     {{#jackson}}
     {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}constructor(baseUrl: String) : this(RestClient.builder()

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-spring-webclient/api.mustache

@@ -21,7 +21,7 @@ import org.springframework.util.LinkedMultiValueMap
 import {{packageName}}.infrastructure.*
 
 {{#operations}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}class {{classname}}(client: WebClient) : ApiClient(client) {
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}open {{/nonPublicApi}}class {{classname}}(client: WebClient) : ApiClient(client) {
 
     {{#jackson}}
     {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}constructor(baseUrl: String) : this(WebClient.builder()

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-vertx/api.mustache

@@ -37,7 +37,7 @@ import {{packageName}}.infrastructure.*
 
 @Suppress ("UNUSED")
 {{#operations}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}class {{classname}}(basePath: kotlin.String = ApiClient.defaultBasePath, accessToken: String? = null, apiKey: MutableMap<String, String> = mutableMapOf(), apiKeyPrefix: MutableMap<String, String> = mutableMapOf(), username: String? = null, password: String? = null, vertx: Vertx): ApiClient(basePath, accessToken, apiKey, apiKeyPrefix, username, password, vertx) {
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}open {{/nonPublicApi}}class {{classname}}(basePath: kotlin.String = ApiClient.defaultBasePath, accessToken: String? = null, apiKey: MutableMap<String, String> = mutableMapOf(), apiKeyPrefix: MutableMap<String, String> = mutableMapOf(), username: String? = null, password: String? = null, vertx: Vertx): ApiClient(basePath, accessToken, apiKey, apiKeyPrefix, username, password, vertx) {
     {{#operation}}
     {{#allParams}}
     {{#isEnum}}

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-volley/api.mustache

@@ -26,7 +26,7 @@ import {{packageName}}.infrastructure.CollectionFormats.*
 * can pass that to the request queue like:
 * Volley.newRequestQueue(context.applicationContext, myCustomHttpStack)
 */
-{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}class {{classname}} (
+{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}open {{/nonPublicApi}}class {{classname}} (
     private val context: Context,
     private val requestQueue: Lazy<RequestQueue> = lazy(initializer = {
         Volley.newRequestQueue(context.applicationContext)

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/apis/AuthApi.kt

@@ -36,7 +36,7 @@ import org.openapitools.client.infrastructure.ResponseType
 import org.openapitools.client.infrastructure.Success
 import org.openapitools.client.infrastructure.toMultiValue
 
-class AuthApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+open class AuthApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     companion object {
         @JvmStatic
         val defaultBasePath: String by lazy {

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/apis/BodyApi.kt

@@ -38,7 +38,7 @@ import org.openapitools.client.infrastructure.ResponseType
 import org.openapitools.client.infrastructure.Success
 import org.openapitools.client.infrastructure.toMultiValue
 
-class BodyApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+open class BodyApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     companion object {
         @JvmStatic
         val defaultBasePath: String by lazy {

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/apis/FormApi.kt

@@ -36,7 +36,7 @@ import org.openapitools.client.infrastructure.ResponseType
 import org.openapitools.client.infrastructure.Success
 import org.openapitools.client.infrastructure.toMultiValue
 
-class FormApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+open class FormApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     companion object {
         @JvmStatic
         val defaultBasePath: String by lazy {

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/apis/HeaderApi.kt

@@ -37,7 +37,7 @@ import org.openapitools.client.infrastructure.ResponseType
 import org.openapitools.client.infrastructure.Success
 import org.openapitools.client.infrastructure.toMultiValue
 
-class HeaderApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+open class HeaderApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     companion object {
         @JvmStatic
         val defaultBasePath: String by lazy {

samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/apis/PathApi.kt

@@ -37,7 +37,7 @@ import org.openapitools.client.infrastructure.ResponseType
 import org.openapitools.client.infrastructure.Success
 import org.openapitools.client.infrastructure.toMultiValue
 
-class PathApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
+open class PathApi(basePath: kotlin.String = defaultBasePath, client: Call.Factory = ApiClient.defaultClient) : ApiClient(basePath, client) {
     companion object {
         @JvmStatic
         val defaultBasePath: String by lazy {