beholder: log partial delivery per-event errors with error_code and reason

[pkcll]

Summary

• Type-assert the send callback error to `*batch.PublishError` so partial delivery failures (individual events rejected server-side while the batch RPC itself succeeded) are logged at WARN with structured `error_code` and `reason` fields.
• Adds `error_code` label to the `chip_ingress.events_dropped` OTel counter for `partial_delivery` failures so dashboards and alerts can track rejection types without relying on logs (e.g. `PUBLISH_ERROR_CODE_VALIDATION_FAILED`).
• Adds `failure_type` attribute (`partial_delivery` vs `rpc_error`) to the same counter to distinguish per-event server rejections from whole-batch RPC failures.
• Whole-batch RPC failures keep the existing ERROR log and increment the counter without `error_code` (no structured server code available).

Jira: INFOPLAT-13901 | Epic: INFOPLAT-7177

Must merge before the chainlink PR that bumps this dep.

Changes

• `pkg/beholder/batch_emitter_service.go`:
  • Type-assert `*batch.PublishError`; WARN log with `error_code`, `reason`, `domain`, `entity`
  • `dropMetricAttrsFor` now accepts `errorCode` — included for `partial_delivery`, omitted for `rpc_error`
• `pkg/beholder/batch_emitter_service_test.go`:
  • `TestChipIngressBatchEmitterService_PartialDeliveryError` — covers log fields (`error_code`, `reason`, `domain`, `entity`) and metric label (`failure_type=partial_delivery`, `error_code=PUBLISH_ERROR_CODE_VALIDATION_FAILED`)

Test plan

• `go test ./pkg/beholder/... -count=1` passes
• Partial delivery log entry is WARN with `error_code` and `reason` fields
• `chip_ingress.events_dropped{failure_type="partial_delivery", error_code="PUBLISH_ERROR_CODE_VALIDATION_FAILED"}` increments for per-event errors
• `chip_ingress.events_dropped{failure_type="rpc_error"}` increments for whole-batch failures (no `error_code` label)

[github-actions]

📊 API Diff Results

No changes detected for module github.com/smartcontractkit/chainlink-common

View full report