release-notes: structure: update 6.4.x
add attribution for community PRs
re-word release note for step refactor to include details about
stricter validation
#### <sub><sup><a name="5833" href="#5833">:link:</a></sup></sub> feature
-* Added a way of renaming pipeline resources while preserving version history by updating the resource name (as well as any reference in steps) and specifying its old name as [**`old_name`**](https://concourse-ci.org/resources.html#schema.resource.old_name). After the pipeline has been configured, the `old_name` field can be removed. #5833
+* @mouellet added a way of renaming pipeline resources while preserving version history by updating the resource name (as well as any reference in steps) and specifying its old name as [**`old_name`**](https://concourse-ci.org/resources.html#schema.resource.old_name). After the pipeline has been configured, the `old_name` field can be removed. #5833
#### <sub><sup><a name="5777" href="#5777">:link:</a></sup></sub> feature
#### <sub><sup><a name="5504" href="#5504">:link:</a></sup></sub> feature
-* Refactor existing step structure to simplify introducing new steps. The primary user facing change are different step validation messages. PR: #5504
+* Refactor existing step structure to simplify introducing new steps. The primary user facing changes are stricter validation and slightly different step validation messages. Previously, fields that were not part of a step wouldn't have failed validation,however, now they will. This will impact stateful actions such as `set-pipeline`. PR: #5504, #5878
#### <sub><sup><a name="5729" href="#5729">:link:</a></sup></sub> feature
