Migrate to DCO

Author: philwebb

Diff for: CONTRIBUTING.adoc

@@ -12,13 +12,9 @@ unacceptable behavior to [email protected].
 
 
 
-== Sign the Contributor License Agreement
-Before we accept a non-trivial patch or pull request we will need you to
-https://cla.pivotal.io/sign/spring[sign the Contributor License Agreement].
-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.  Active contributors might be asked to join the core team, and
-given the ability to merge pull requests.
+== Include a Signed Off By Trailer
+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 https://spring.io/blog/2025/01/06/hello-dco-goodbye-cla-simplifying-contributions-to-spring[Hello DCO, Goodbye CLA: Simplifying Contributions to Spring].