feat(connectors): retry transient Doris Stream Load failures in-request

[ryankert01]

Which issue does this PR address?

Relates to #3215

Rationale

Follow-up to the Doris sink (#3215). The connector already classified transient Stream Load outcomes as retryable but had no retry path, so under the runtime's at-most-once delivery a transient backend blip silently dropped the batch.

What changed?

The Doris sink classified transient Stream Load outcomes (5xx/408/429, transport errors, Publish Timeout) as CannotStoreData but never retried them: the runtime commits the consumer offset at poll time before consume() runs and discards its return value, so a transient failure dropped the batch with no replay.

consume() now retries a transiently-failed batch in-request via a new load_batch() that wraps send plus status classification, re-PUTing under the same deterministic label so Doris dedupes a prior attempt that actually landed (e.g. a 2xx whose body could not be read). Permanent failures (4xx, Fail, schema/redirect problems) are never retried. Backoff and jitter come from iggy_connector_sdk::retry, bounded by new max_retries/retry_delay/max_retry_delay config (defaults 3 / 200ms / 5s). This shrinks the at-most-once window within a single poll; cross-poll and crash delivery stay a runtime concern.

Local Execution

• Passed
• Pre-commit hooks: checks run manually. The license-headers hook cannot execute on this machine (its script needs bash 4+ mapfile; only bash 3.2 is present), but hawkeye check passes directly and CI enforces it. markdownlint, taplo, cargo fmt, cargo clippy -p iggy_connector_doris_sink --all-targets -- -D warnings, and cargo test -p iggy_connector_doris_sink (41 tests) all pass.

AI Usage

1. Claude Code (Anthropic).
2. Implemented the retry loop, config plumbing, tests, and README/config updates, after verifying the runtime's at-most-once delivery semantics directly in the runtime source.
3. Three new wiremock unit tests pin the behavior: transient-then-success (retry fires), exhausted-budget (exact attempt count via .expect), and permanent-not-retried. Full crate suite, clippy, and doc lint pass locally.
4. Yes.

[github-actions]

Thanks for the PR. It is labeled S-waiting-on-review and queued for review.

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See CONTRIBUTING.md for details.

[codecov]

Codecov Report

❌ Patch coverage is 93.10345% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.37%. Comparing base (307fdb1) to head (549e171).

Files with missing lines	Patch %	Lines
core/connectors/sinks/doris_sink/src/lib.rs	93.10%	5 Missing and 3 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3574       +/-   ##
=============================================
- Coverage     74.07%   46.37%   -27.70%     
  Complexity      937      937               
=============================================
  Files          1249     1246        -3     
  Lines        128248   111821    -16427     
  Branches     104116    87689    -16427     
=============================================
- Hits          94994    51853    -43141     
- Misses        30219    57300    +27081     
+ Partials       3035     2668      -367     

Components	Coverage Δ
Rust Core	39.10% <93.10%> (-35.61%)	⬇️
Java SDK	62.44% <ø> (ø)
C# SDK	72.06% <ø> (ø)
Python SDK	88.88% <ø> (ø)
PHP SDK	84.29% <ø> (ø)
Node SDK	91.35% <ø> (ø)
Go SDK	40.14% <ø> (ø)

Files with missing lines	Coverage Δ
core/connectors/sinks/doris_sink/src/lib.rs	93.12% <93.10%> (+0.77%)	⬆️

... and 352 files with indirect coverage changes

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