Add comment about spark.addArtifact()

Author: razvan

tests/templates/kuttl/spark-connect-kerberos/10_spark-connect.yaml.j2

@@ -151,7 +151,7 @@ spec:
         # protocol (not the rename-based FileOutputCommitter), so writes to S3
         # work without the staging/_temporary issues of plain parquet tables.
         # The catalog inherits the kerberos metastore config from spark.hadoop.*
-        # above. See https://github.com/stackabletech/spark-k8s-operator/issues/702
+        # above. See https://issues.apache.org/jira/browse/SPARK-46032
         spark.sql.extensions: org.apache.iceberg.spark.extensions.IcebergSparkSessionExtensions
         spark.sql.catalog.iceberg: org.apache.iceberg.spark.SparkCatalog
         spark.sql.catalog.iceberg.type: hive

tests/templates/kuttl/spark-connect-kerberos/20-run-connect-client.yaml.j2

@@ -63,10 +63,12 @@ data:
       # metastore query (driver-side). We deliberately avoid result.collect() /
       # count() over the Iceberg table: a *distributed* scan ships the Iceberg
       # RDD closure to the executors, where it currently fails to deserialize on
-      # Spark Connect ("cannot assign SerializedLambda ... Function3"). That is a
-      # Spark Connect classloader limitation independent of where the Iceberg jar
-      # is placed, and is separate from the metastore/Kerberos integration this
-      # test validates. See https://github.com/stackabletech/spark-k8s-operator/issues/702
+      # Spark Connect ("cannot assign SerializedLambda ... Function3"). This is an
+      # upstream Spark Connect classloader limitation (see SPARK-46032 /
+      # SPARK-51537) independent of how the Iceberg jar is provisioned - it
+      # reproduces with --packages, with the jar on the system classpath, with
+      # spark.addArtifact(), and with --packages + addArtifact together - and is
+      # separate from the metastore/Kerberos integration this test validates.
       ice_tables = [row.tableName for row in spark.sql("SHOW TABLES IN iceberg.lakehouse").collect()]
       print("Tables in 'iceberg.lakehouse':", ice_tables)
       assert "greetings" in ice_tables, f"Iceberg table not registered in the HMS: {ice_tables}"