test: verify upstream errors are relayed to client in streaming chatcompletions

[ssncferreira]

Description

Adds unit tests to verify that upstream provider errors are correctly relayed to clients before streaming starts.
This was introduced after testing with providers where 429 (rate limit) responses appeared to be ignored. Investigation confirmed that aibridge was correctly relaying these errors, the issue was on the client side. These tests document and verify this behavior.

Changes

• Added TestStreamingInterception_RelaysUpstreamErrorToClient
• Tests cover 400 (bad request), 429 (rate limit), and 500 (internal server error) responses

[ssncferreira]

• test: verify upstream errors are relayed to client in streaming chatcompletions #148 👈 (View in Graphite)
• main

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[dannykopping]

Thanks!

[pawbana]

Would be nice to have similar test for blocking.

[ssncferreira]

Would be nice to have similar test for blocking.

True, and also for OpenAI's responses and Anthropic's messages. We can address those in follow-up PRs. I added this one because while testing the Copilot provider, it seemed like aibridge wasn't forwarding 429 responses to the client. Turned out the client was ignoring them. Added this test to confirm aibridge was correctly forwarding the error.