[kotlin] Add OkHttpClient.Builder to ApiClient. (#7907)

Author: ejithon

modules/swagger-codegen/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache

@@ -12,7 +12,12 @@ open class ApiClient(val baseUrl: String) {
         protected val XmlMediaType = "application/xml"
 
         @JvmStatic
-        val client : OkHttpClient = OkHttpClient()
+        val client by lazy {
+            builder.build()
+        }
+
+        @JvmStatic
+        val builder: OkHttpClient.Builder = OkHttpClient.Builder()
 
         @JvmStatic
         var defaultHeaders: Map<String, String> by ApplicationDelegates.setOnce(mapOf(ContentType to JsonMediaType, Accept to JsonMediaType))

samples/client/petstore/kotlin-string/src/main/kotlin/io/swagger/client/infrastructure/ApiClient.kt

@@ -12,7 +12,12 @@ open class ApiClient(val baseUrl: String) {
         protected val XmlMediaType = "application/xml"
 
         @JvmStatic
-        val client : OkHttpClient = OkHttpClient()
+        val client by lazy {
+            builder.build()
+        }
+
+        @JvmStatic
+        val builder: OkHttpClient.Builder = OkHttpClient.Builder()
 
         @JvmStatic
         var defaultHeaders: Map<String, String> by ApplicationDelegates.setOnce(mapOf(ContentType to JsonMediaType, Accept to JsonMediaType))

samples/client/petstore/kotlin-threetenbp/src/main/kotlin/io/swagger/client/infrastructure/ApiClient.kt

@@ -12,7 +12,12 @@ open class ApiClient(val baseUrl: String) {
         protected val XmlMediaType = "application/xml"
 
         @JvmStatic
-        val client : OkHttpClient = OkHttpClient()
+        val client by lazy {
+            builder.build()
+        }
+
+        @JvmStatic
+        val builder: OkHttpClient.Builder = OkHttpClient.Builder()
 
         @JvmStatic
         var defaultHeaders: Map<String, String> by ApplicationDelegates.setOnce(mapOf(ContentType to JsonMediaType, Accept to JsonMediaType))

samples/client/petstore/kotlin/src/main/kotlin/io/swagger/client/infrastructure/ApiClient.kt

@@ -12,7 +12,12 @@ open class ApiClient(val baseUrl: String) {
         protected val XmlMediaType = "application/xml"
 
         @JvmStatic
-        val client : OkHttpClient = OkHttpClient()
+        val client by lazy {
+            builder.build()
+        }
+
+        @JvmStatic
+        val builder: OkHttpClient.Builder = OkHttpClient.Builder()
 
         @JvmStatic
         var defaultHeaders: Map<String, String> by ApplicationDelegates.setOnce(mapOf(ContentType to JsonMediaType, Accept to JsonMediaType))