feat(cpp): Add functions related to consumer groups

[slbotbm]

Which issue does this PR close?

Works towards completion of #2763

Rationale

Additions to the cpp bindings to make it feature complete.

What changed?

Add consumer-group creating and deletion functions. Also adds commented out purge_topic and purge_stream but those require the ability to actually send messages to the server, which is not yet implemented. Will be added once they can be tested. Also adds create_partition, delete_partitions, and functions that allow cpp user to directly create identifiers instead of manually defining everything.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. codex
2. code generation
3. manual planning and inspection, local execution
4. Can you explain every line of the code if asked? Yes

[slbotbm]

This PR is ready for review.

[amlel-el-mahrouss]

Here's my first review @slbotbm, let me know your reply by pinging me

[slbotbm]

Converting this to a draft since I would like to think a little more deeply about the API we will be exposing.

[slbotbm]

This PR is ready for review. I was unsure of how to expose the consumer interface to the user, and decided that an additional opaque consumer type will be necessary (to be done in a future PR). The client can now only create or delete consumer groups, but cannot join or read from them. The consumers will be able to join and leave the groups, and also read messages. The lifetimes and safety guarantees of this additional type will still need to be thought through, though.