[kotlin][spring-webclient] Add parseDateToQueryString (#16069)

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

@@ -53,3 +53,20 @@ open class ApiClient(protected val client: WebClient) {
     private fun <I : Any> WebClient.RequestBodySpec.body(requestConfig: RequestConfig<I>) =
         apply { if (requestConfig.body != null) bodyValue(requestConfig.body) }
 }
+
+inline fun <reified T: Any> parseDateToQueryString(value : T): String {
+        {{#toJson}}
+        /*
+        .replace("\"", "") converts the json object string to an actual string for the query parameter.
+        The moshi or gson adapter allows a more generic solution instead of trying to use a native
+        formatter. It also easily allows to provide a simple way to define a custom date format pattern
+        inside a gson/moshi adapter.
+        */
+        {{#jackson}}
+        return Serializer.jacksonObjectMapper.writeValueAsString(value).replace("\"", "")
+        {{/jackson}}
+        {{/toJson}}
+        {{^toJson}}
+        return value.toString()
+        {{/toJson}}
+    }

samples/client/petstore/kotlin-jvm-spring-2-webclient/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -53,3 +53,13 @@ open class ApiClient(protected val client: WebClient) {
     private fun <I : Any> WebClient.RequestBodySpec.body(requestConfig: RequestConfig<I>) =
         apply { if (requestConfig.body != null) bodyValue(requestConfig.body) }
 }
+
+inline fun <reified T: Any> parseDateToQueryString(value : T): String {
+        /*
+        .replace("\"", "") converts the json object string to an actual string for the query parameter.
+        The moshi or gson adapter allows a more generic solution instead of trying to use a native
+        formatter. It also easily allows to provide a simple way to define a custom date format pattern
+        inside a gson/moshi adapter.
+        */
+        return Serializer.jacksonObjectMapper.writeValueAsString(value).replace("\"", "")
+    }

samples/client/petstore/kotlin-jvm-spring-3-webclient/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -53,3 +53,13 @@ open class ApiClient(protected val client: WebClient) {
     private fun <I : Any> WebClient.RequestBodySpec.body(requestConfig: RequestConfig<I>) =
         apply { if (requestConfig.body != null) bodyValue(requestConfig.body) }
 }
+
+inline fun <reified T: Any> parseDateToQueryString(value : T): String {
+        /*
+        .replace("\"", "") converts the json object string to an actual string for the query parameter.
+        The moshi or gson adapter allows a more generic solution instead of trying to use a native
+        formatter. It also easily allows to provide a simple way to define a custom date format pattern
+        inside a gson/moshi adapter.
+        */
+        return Serializer.jacksonObjectMapper.writeValueAsString(value).replace("\"", "")
+    }