Add deprecated message for micronaut generator and links to actual micronaut generator

Author: altro3

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

@@ -712,4 +712,22 @@ public void setSerializationLibrary(final String serializationLibrary) {
             throw new RuntimeException(sb.toString());
         }
     }
+
+    @Override
+    public void postProcess() {
+        System.out.println("################################################################################");
+        System.out.println("# Thanks for using OpenAPI Generator.                                          #");
+        System.out.println("# Please consider donation to help us maintain this project \uD83D\uDE4F                 #");
+        System.out.println("# https://opencollective.com/openapi_generator/donate                          #");
+        System.out.println("#                                                                              #");
+        System.out.println("# WARNING! This generator is outdated. Please use the official generator for   #");
+        System.out.println("# Micronaut: https://github.com/micronaut-projects/micronaut-openapi with the  #");
+        System.out.println("# help of the plugin for gradle                                                #");
+        System.out.println("# (https://github.com/micronaut-projects/micronaut-gradle-plugin) and maven    #");
+        System.out.println("# (https://github.com/micronaut-projects/micronaut-maven-plugin).              #");
+        System.out.println("#                                                                              #");
+        System.out.println("# Supported generators for micronaut client / server side, java and kotlin     #");
+        System.out.println("# languages.                                                                   #");
+        System.out.println("################################################################################");
+    }
 }