[kotlin] Simplify default value template logic per PR review

Move defaultValue outside required-check since it always applies,
simplify nullable/default patterns in jvm-ktor api.mustache and
javalin5/javalin6 service.mustache templates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: halotukozak

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

@@ -52,7 +52,7 @@ import com.fasterxml.jackson.databind.ObjectMapper
         {{#returnType}}
             @Suppress("UNCHECKED_CAST")
         {{/returnType}}
-        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{#required}}{{#defaultValue}} = {{{defaultValue}}}{{/defaultValue}}{{/required}}{{^required}}?{{#defaultValue}} = {{{defaultValue}}}{{/defaultValue}}{{^defaultValue}} = null{{/defaultValue}}{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}> {
+        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}> {
 
             val localVariableAuthNames = listOf<String>({{#authMethods}}"{{name}}"{{^-last}}, {{/-last}}{{/authMethods}})
 

modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache

@@ -27,7 +27,7 @@ interface {{classname}}Service {
     {{/externalDocs}}
      * @see {{classname}}#{{operationId}}
      */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^required}}{{^defaultValue}} = null{{/defaultValue}}{{#defaultValue}} = {{{defaultValue}}}{{/defaultValue}}{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}
 {{/operation}}
 }
 {{/operations}}

modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache

@@ -29,7 +29,7 @@ interface {{classname}}Service {
     {{/externalDocs}}
      * @see {{classname}}#{{operationId}}
      */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^required}}{{^defaultValue}} = null{{/defaultValue}}{{#defaultValue}} = {{{defaultValue}}}{{/defaultValue}}{{/required}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}
 {{/operation}}
 }
 {{/operations}}