Dart generator: Add default value for optional params

Author: Daniel Jibouleau

modules/openapi-generator/src/main/resources/dart2/api.mustache

@@ -49,7 +49,7 @@ class {{{classname}}} {
   ///
     {{/-last}}
   {{/allParams}}
-  Future<Response> {{{nickname}}}WithHttpInfo({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}}? {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
+  Future<Response> {{{nickname}}}WithHttpInfo({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}}? {{{paramName}}}{{#defaultValue}} = {{{.}}}{{/defaultValue}},{{^-last}} {{/-last}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
     // ignore: prefer_const_declarations
     final path = r'{{{path}}}'{{#pathParams}}
       .replaceAll({{=<% %>=}}'{<% baseName %>}'<%={{ }}=%>, {{{paramName}}}{{^isString}}.toString(){{/isString}}){{/pathParams}};
@@ -161,7 +161,7 @@ class {{{classname}}} {
   ///
     {{/-last}}
   {{/allParams}}
-  Future<{{#returnType}}{{{.}}}?{{/returnType}}{{^returnType}}void{{/returnType}}> {{{nickname}}}({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}}? {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
+  Future<{{#returnType}}{{{.}}}?{{/returnType}}{{^returnType}}void{{/returnType}}> {{{nickname}}}({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}}? {{{paramName}}}{{#defaultValue}} = {{{.}}}{{/defaultValue}},{{^-last}} {{/-last}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
     final response = await {{{nickname}}}WithHttpInfo({{#allParams}}{{#required}}{{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}}{{#hasOptionalParams}} {{#allParams}}{{^required}}{{{paramName}}}: {{{paramName}}},{{^-last}} {{/-last}}{{/required}}{{/allParams}} {{/hasOptionalParams}});
     if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, await _decodeBodyBytes(response));