Review decoders and message readers [SPR-17418]

[spring-projects-issues]

Arjen Poutsma opened SPR-17418 and commented

Review decoders and message readers for both error and cancellation signals.

---

This issue is a sub-task of #21941

[spring-projects-issues]

Arjen Poutsma commented

Fixed in f738273 946ec7e, added tests in a37efc9 47fe050 0176d36