bug(Rust SDK): IggyConsumer::next() after shutdown() hangs or silently drops offsets

[haubur]

Bug description

Description
When calling shutdown() on the IggyConsumer polling is still possible with next() but causes unintended behavior for:

1. standalone consumer next() still consumes messages from buffer or server, while sending offsets is prevented due to dropping the channel in shutdown()
2. a consumer group member after shutdown can still call next but hangs indefinitely:

   iggy/core/sdk/src/clients/consumer.rs

   Line 695 in 6043d19

   while !can_poll.load(ORDERING)

Calling init() again is idempotent, so a user cannot recover from this state.

Options

• make poll_next() check shutdown() and return
• None to respect the Stream trait
• IggyError that can be handled by the user (preferred)

Affected area / component

Rust SDK

Deployment

None

Versions

No response

Hardware / environment

No response

Sample code

No response

Logs

No response

Iggy server config

No response

Reproduction

No response

Contribution

• I'm willing to submit a pull request to fix this bug

Good first issue

• I think this could be a good first issue for a new contributor