adds support for x-pattern-message in kotlin-spring generator (#19134)

* adds support for x-pattern-message for patterns in kotlin-spring generator as known in java spring generator

* updates doc kotlin-spring

Author: orolhawion

docs/generators/kotlin-spring.md

@@ -57,6 +57,13 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |useSwaggerUI|Open the OpenApi specification in swagger-ui. Will also import and configure needed dependencies| |true|
 |useTags|Whether to use tags for creating interface and controller class names| |false|
 
+## SUPPORTED VENDOR EXTENSIONS
+
+| Extension name | Description | Applicable for | Default value |
+| -------------- | ----------- | -------------- | ------------- |
+|x-pattern-message|Add this property whenever you need to customize the invalidation error message for the regex pattern of a variable|FIELD, OPERATION_PARAMETER|null
+
+
 ## IMPORT MAPPING
 
 | Type/Alias | Imports |

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java

@@ -32,6 +32,7 @@
 import org.openapitools.codegen.CodegenResponse;
 import org.openapitools.codegen.CodegenType;
 import org.openapitools.codegen.SupportingFile;
+import org.openapitools.codegen.VendorExtension;
 import org.openapitools.codegen.languages.features.BeanValidationFeatures;
 import org.openapitools.codegen.languages.features.DocumentationProviderFeatures;
 import org.openapitools.codegen.languages.features.SwaggerUIFeatures;
@@ -982,4 +983,11 @@ public void setRequestMappingMode(RequestMappingMode requestMappingMode) {
         this.requestMappingMode = requestMappingMode;
     }
 
+    @Override
+    public List<VendorExtension> getSupportedVendorExtensions() {
+        List<VendorExtension> extensions = super.getSupportedVendorExtensions();
+        extensions.add(VendorExtension.X_PATTERN_MESSAGE);
+        return extensions;
+    }
+
 }

modules/openapi-generator/src/main/resources/kotlin-spring/beanValidationModel.mustache

@@ -4,7 +4,7 @@ format: email
     @get:Email{{/isEmail}}{{!
 pattern set
 }}{{#pattern}}
-    @get:Pattern(regexp="{{{.}}}"){{/pattern}}{{!
+    @get:Pattern(regexp="{{{pattern}}}"{{#vendorExtensions.x-pattern-message}}, message="{{vendorExtensions.x-pattern-message}}"{{/vendorExtensions.x-pattern-message}}){{/pattern}}{{!
 minLength && maxLength set
 }}{{#minLength}}{{#maxLength}}
     @get:Size(min={{minLength}},max={{maxLength}}){{/maxLength}}{{/minLength}}{{!