fix: add bounds check for partition index int32 conversion

[merlimat]

Motivation

CodeQL code-scanning alert #1 (go/incorrect-integer-conversion, high — CWE-190 / CWE-681) flags pulsar/consumer_partition.go:422, where the partition index — ultimately parsed from the topic name via strconv.Atoi in getPartitionIndex — is converted from int to int32 without a bounds check.

Modifications

Add an explicit range check in newPartitionConsumer before the int32(options.partitionIdx) conversion, returning an error if the value falls outside the int32 range. Negative values (e.g. -1 for non-partitioned topics) remain valid.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework without new test coverage; the conversion is exercised by the existing partitioned-consumer tests.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no

Documentation

• Does this pull request introduce a new feature? no