improve generated header text

Author: hauner

src/main/groovy/com/github/hauner/openapi/spring/writer/java/HeaderWriter.groovy

@@ -17,6 +17,9 @@
 package com.github.hauner.openapi.spring.writer.java
 
 import com.github.hauner.openapi.core.writer.java.SimpleWriter
+import io.openapiprocessor.spring.Version
+
+import java.time.Instant
 
 /**
  * Writer for a simple header of the generated interfaces & classes.
@@ -27,8 +30,11 @@ class HeaderWriter implements SimpleWriter {
 
     static String HEADER = """\
 /*
- * This class is auto generated by https://github.com/hauner/openapi-processor-spring.
- * DO NOT EDIT.
+ * DO NOT MODIFY - this class was auto generated by openapi-processor-spring
+ *
+ * ${Version.version}
+ * ${Instant.now().toString()} 
+ * https://docs.openapiprocessor.io/spring 
  */
 
 """