feat: add cdr processing worker and dlq routing

src/core/worker/processor.py

@@ -0,0 +1,38 @@
+import json
+from typing import Any
+
+from core.domain.errors import (
+    CDRProcessingError,
+    FailureReason,
+)
+from core.domain.models import NormalizedCDR
+from core.domain.normalization import normalize_cdr
+from core.domain.validation import parse_raw_cdr
+
+
+def decode_payload(value: bytes) -> dict[str, Any]:
+    try:
+        text = value.decode("utf-8")
+        payload = json.loads(text)
+
+    except (UnicodeDecodeError, json.JSONDecodeError) as exc:
+        raise CDRProcessingError(
+            reason=FailureReason.MALFORMED_JSON,
+            detail=f"Unable to decode Kafka message as JSON: {exc}",
+        ) from exc
+
+    if not isinstance(payload, dict):
+        raise CDRProcessingError(
+            reason=FailureReason.NORMALIZATION_ERROR,
+            detail="Kafka JSON payload must be an object.",
+        )
+
+    return payload
+
+
+def process_payload(
+    payload: dict[str, Any],
+) -> NormalizedCDR:
+    raw_cdr = parse_raw_cdr(payload)
+
+    return normalize_cdr(raw_cdr)