[fix][client] handle subscriptionRolePrefix properly

[candu]

Fixes #415

Motivation

At my current employer, we have a centrally-managed Pulsar cluster that requires use of a pre-assigned subscriptionRolePrefix for your client when creating a reader.

As per docs, you should be able to do this with:

client.createReader({ topic, startMessageId: Pulsar.MessageId.earliest(), subscriptionRolePrefix: subscriptionPrefix, }); 

However, this bug prevents that from working correctly.

Modifications

Small change in ReaderConfig.cc to call the correct PULSAR_PUBLIC function.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage. That said: I did test that, by using my patched client, I can create a reader in our internal setup described above. (Without the patch, it fails.)

(Due to NDA, I can't describe that setup in more detail, sadly.)

Documentation

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• doc-not-needed
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Docs are not needed: this fixes a feature that is already documented, but which did not previously work as intended.

[shibd]

Nice catch!