Add regression tests for null and duplicate type fields in provider-message decoder - #18

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: aws-actions/configure-aws-credentials@cabfdba3510de1431bac9dba27511d97497fc100. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/