feat(utils): retry transient upstream errors in rest_query/post_query

[Elarwei001]

Scope

rest_query / post_query in gget/utils.py are the shared entry points for every Ensembl-backed module (seq, ref, search, info, blat, and enrichr with ensembl=True). They currently issue a single request, so any transient hiccup from the upstream service fails the whole call. Ensembl REST in particular returns intermittent 500/502/503/504 or 429 under load, and occasionally drops the connection — which shows up as flaky failures in CI and for users.

Change

Add a small _query_with_retry helper and route both functions through it:

• Retries on 429 and 5xx (500/502/503/504) and on connection/timeout errors, with linear backoff (2s, 4s, 6s; 4 attempts total).
• Honors Retry-After when the server sends one (capped at 30s).
• Does not retry 4xx client errors (e.g. 404) — returned to the caller unchanged, so existing error handling (if not r.ok: raise ...) is preserved.
• After exhausting retries, returns the last response (or re-raises the last connection error), so callers behave exactly as before in the terminal-failure case.

No public API or return types change — this only adds resilience underneath the existing functions.

Tests

Offline unit tests (tests/test_utils.py::TestQueryRetry, mocked requests/sleep — no network) cover: success after retry, connection-error retry, no-retry on 404, retry exhaustion, and Retry-After handling.

Notes

utils.py already has an http_json retry helper, but it always parses JSON and raises on non-JSON bodies. rest_query can return either text or JSON and needs the raw Response, so this helper returns the Response object and leaves body handling to the existing call sites.

[Elarwei001]

CI keeps fail on external service's 5xx error, add retry to increase robustness.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.66%. Comparing base (e43a804) to head (85d2124).
⚠️ Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #261      +/-   ##
==========================================
- Coverage   56.70%   56.66%   -0.05%     
==========================================
  Files          29       29              
  Lines        9392     9417      +25     
==========================================
+ Hits         5326     5336      +10     
- Misses       4066     4081      +15     

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