fix: normalize conflict struct columns in OTLP sink before encoding

[Copilot]

OtlpSink::encode_batch silently dropped any Arrow Struct-typed column via DataType::Struct(_) => continue, causing data loss for fields with mixed types (which the conflict schema mechanism encodes as Struct).

Changes

• logfwd-arrow: Moved conflict_schema module here from logfwd-transform so it's accessible to output crates without a circular dependency
• logfwd-transform: Re-exports logfwd_arrow::conflict_schema for backward compatibility
• logfwd-output: Added logfwd-arrow dependency; calls normalize_conflict_columns on the batch before the encoding loop so conflict Struct columns are flattened to Utf8 rather than skipped

// Before: silently dropped
DataType::Struct(_) => continue,

// After: normalize first, then encode as Utf8
let batch = normalize_conflict_columns(&batch)?;
// ... encoding loop now sees Utf8 columns

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository YAML (base), Organization UI (inherited)

Review profile: ASSERTIVE

Plan: Free

Run ID: 065b9674-d0d5-4338-86aa-f384db650fad

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• ✅ Review completed - (🔄 Check again to review again)

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}