Fix #2868: Add topicHeaderName to timestamp-router-action kamelet

The CAMEL-23584 rename of kafka.TOPIC to CamelKafkaTopic broke the
kafka-router-pipe integration test because HTTP components filter
Camel*-prefixed headers from incoming requests. Adding an optional
topicHeaderName property lets the test (and users) specify which
header carries the topic name, falling back to CamelKafkaTopic.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: davsclaus

kamelets/timestamp-router-action.kamelet.yaml

@@ -47,6 +47,10 @@ spec:
         description: The name of the header containing a timestamp
         type: string
         default: "kafka.TIMESTAMP"
+      topicHeaderName:
+        title: Topic Header Name
+        description: The name of the header containing the topic name. When not set, the default Kafka topic header (CamelKafkaTopic) is used.
+        type: string
     type: object
   dependencies:
   - "camel:kamelet"
@@ -65,4 +69,7 @@ spec:
       - setProperty:
           name: "timestampHeaderName"
           constant: "{{timestampHeaderName}}"
+      - setProperty:
+          name: "topicHeaderName"
+          constant: "{{?topicHeaderName}}"
       - bean: "org.apache.camel.component.kafka.transform.TimestampRouter"

tests/camel-kamelets-itest/src/test/resources/kafka/kafka-router-pipe.yaml

@@ -35,6 +35,7 @@ spec:
       properties:
         topicFormat: $[topic]_$[timestamp]
         timestampFormat: YYYY-MM-dd
+        topicHeaderName: kafka.TOPIC
     - ref:
         kind: Kamelet
         apiVersion: camel.apache.org/v1