Keep Nango error bodies so expired Outlook tokens reconnect

[ComputelessComputer]

Summary

Problem: 0.0.78 still returned 500 on Outlook list-events (~21s). Nango exhausts 401 retries and responds 500; error_for_status discarded the body, so we never saw InvalidAuthenticationToken / invalid_credentials and never marked reconnect.

Fix: Proxy errors now include status + body. Auth detection also matches Nango refresh failures (invalid_credentials, could not refresh). Generic 500s stay 500s.

Verification

• cargo test -p nango --lib
• cargo test -p api-nango --lib detects_graph_expired_token

---

Note

Medium Risk
Changes Nango proxy error handling and calendar auth-failure detection for all Google/Outlook list routes; misclassification could wrongly trigger reconnect or still return 500, but scope is limited to integration HTTP clients with added tests.

Overview
Fixes calendar list endpoints returning slow 500 responses instead of 424 reconnect when Nango/Graph auth fails after retries.

Nango HTTP layer: Proxy responses no longer use error_for_status(), which dropped error bodies. Failed responses are read via response_bytes and surfaced as Error::Api(status, body) so downstream code can inspect provider/Nango payloads (including 500 responses that still carry auth JSON).

Auth classification: is_provider_auth_failure now matches additional message shapes (status 401, invalid_credentials, refresh-token failures) so map_provider_error can mark connections reconnect-required instead of treating them as generic internal errors.

Calendar routes: Google and Outlook list-calendars/list-events HTTP clients call with_retries(0) to avoid long Nango retry loops on bad tokens (~21s) while still benefiting from preserved error bodies.

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