Polish README.md and CONTRIBUTING.adoc

Signed-off-by: Tran Ngoc Nhan <[email protected]>

Author: ngocnhan-tran1996

CONTRIBUTING.adoc

@@ -32,7 +32,7 @@ For additional details, please refer to the blog post https://spring.io/blog/202
 
 1. Go to https://github.com/spring-projects/spring-kafka[https://github.com/spring-projects/spring-kafka]
 2. Hit the "fork" button and choose your own GitHub account as the target
-3. For more detail see https://help.github.com/fork-a-repo/[Fork A Repo].
+3. For more detail see https://help.github.com/articles/fork-a-repo/[Fork A Repo].
 
 == Setup your Local Development Environment
 
@@ -153,7 +153,7 @@ Please carefully follow the whitespace and formatting conventions already presen
 [source, java]
 ----
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2025-present the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -171,26 +171,9 @@ Please carefully follow the whitespace and formatting conventions already presen
 package ...;
 ----
 
-== Update license header to modified files as necessary
+== Use `@since` tags
 
-Always check the date range in the Apache license header. For example, if you've modified a file in 2016 whose header
-still reads
-
-[source java]
-----
- * Copyright 2002-2011 the original author or authors.
-----
-
-then be sure to update it to 2016 appropriately
-
-[source java]
-----
- * Copyright 2002-2016 the original author or authors.
-----
-
-== Use @since tags
-
-Use @since tags for newly-added public API types and methods e.g.
+Use `@since` tags for newly-added public API types and methods e.g.
 
 [source java]
 ----

README.md

@@ -71,10 +71,10 @@ Please help out on the [StackOverflow](https://stackoverflow.com/questions/tagge
 * Create [GitHub issues](https://github.com/spring-projects/spring-kafka/issues) for bugs and new features and comment and vote on the ones that you are interested in.
 * GitHub is for social coding: if you want to write code, we encourage contributions through pull requests from [forks of this repository](https://help.github.com/forking/).  
 If you want to contribute code this way, please reference a GitHub issue as well covering the specific issue you are addressing.
-* Watch for upcoming articles on Spring by [subscribing](https://www.springsource.org/node/feed) to springframework.org
 
-Before we accept a non-trivial patch or pull request we will need you to sign the [contributor's agreement](https://support.springsource.com/spring_committer_signup).
-Signing the contributor's agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do.
+All commits must include a _Signed-off-by_ trailer at the end of each commit message to indicate that the contributor agrees to the Developer Certificate of Origin.
+For additional details, please refer to the blog post [Hello DCO, Goodbye CLA: Simplifying Contributions to Spring](https://spring.io/blog/2025/01/06/hello-dco-goodbye-cla-simplifying-contributions-to-spring).
+The DCO does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do.
 Active contributors might be asked to join the core team and given the ability to merge pull requests.
 
 ## Code Conventions and Housekeeping
@@ -95,4 +95,4 @@ Use the [`spring-kafka` tag on Stack Overflow](https://stackoverflow.com/questio
 
 # License
 
-Spring Kafka is released under the terms of the Apache Software License Version 2.0 (see LICENSE.txt).
+Spring Kafka is released under the terms of the Apache Software License Version 2.0 (see [LICENSE.txt](LICENCE.txt)).