feat: implement json.Marshaler for CLEFEvent

[desertwitch]

Summary by CodeRabbit

• New Features

  • Implemented custom JSON serialization for CLEF events with improved field omission and property handling.

• Bug Fixes

  • Fixed README examples for file path handling and OpenTelemetry imports.

• Tests

  • Added comprehensive test suite for event encoding and JSON marshaling.

• Documentation

  • Added v0.8.1 changelog entry and improved inline documentation.

• Chores

  • Updated test tool dependency version.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b69cda52-a4d9-42be-bf96-dd587c4216c2

📥 Commits

Reviewing files that changed from the base of the PR and between 6b93acc and fc898b8.

📒 Files selected for processing (4)

• CONTRIBUTING.md
• LICENSE
• SECURITY.md
• handler.go

Walkthrough

CLEFEvent replaces struct-tag JSON serialization with a custom MarshalJSON backed by encodeEvent, dottedToNested, and addNested helpers. sendEvents in the flusher is rewritten to stream JSON directly via json.Encoder. Comprehensive tests are added for all new encoding logic, and documentation comments are expanded across handler.go, flusher.go, seqotel/seqotel.go, and README.md.

Changes

CLEFEvent custom marshaling and flusher integration

Layer / File(s)	Summary
CLEFEvent struct and custom MarshalJSON implementation event.go	CLEFEvent struct tags are removed and MarshalJSON is added, delegating to encodeEvent, which builds the CLEF JSON object by copying Properties, escaping @-prefixed user keys, always emitting @t, and conditionally emitting @m, @l, @x, @st, @tr, @sp, @ps, @ra, and @sk. dottedToNested and addNested helpers convert dotted ResourceAttributes keys into nested maps for the @ra field.
encodeEvent, dottedToNested, and addNested test coverage event_test.go	New test file covers required CLEF keys, all conditional optional fields (exception, trace/span IDs, parent span ID, span start, span kind), property copying with reserved-key override precedence, @-sign escaping and no-double-escape, MarshalJSON round-trip, dottedToNested across all key shapes and conflict cases, and addNested for all path and merge scenarios.
sendEvents rewrite: direct json.Encoder body construction flusher.go, flusher_test.go	sendEvents is rewritten to encode all events into a strings.Builder via a shared json.Encoder instead of per-event intermediate buffers. Error messages for request construction and transport failures are wrapped with fmt.Errorf. Oversized-event drop logging includes the HTTP status code. Non-2xx responses log a status-code-prefixed message and trigger retry. flusher_test.go adds assertions that unencodable events skip the HTTP call and invoke the error callback.
Documentation comments, README fixes, changelog, and dependency bump handler.go, flusher.go, seqotel/seqotel.go, README.md, CHANGELOG.md, .changes/v0.8.1.md, tool/tester/go.mod	GoDoc comments are added or expanded on newHTTPClient, runFlusher, flushBatch, SeqHandler.start, SeqHandler.Close, resolveAndAddAttr, convertLevel, shared, worker, and seqotel helpers. README examples are corrected (filepath.Base, OTel imports). Changelog entries record the new json.Marshaler. tool/tester/go.mod bumps the slog-seq dependency to v0.8.0.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: implementing json.Marshaler for CLEFEvent, which is the primary functional addition across the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Create PR with unit tests
• Commit unit tests in branch devel

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[coderabbitai]

Actionable comments posted: 3

🧹 Nitpick comments (1)

event.go (1)

93-98: 💤 Low value

Modifying map during iteration is safe here but fragile.

The escaping loop modifies topLevel while iterating. This works because newly added @@-prefixed keys are excluded by the condition, but the pattern is subtle and could break if the logic changes.

Consider iterating over a snapshot of the keys or the original e.Properties:

♻️ Suggested alternative

-	// Escape any @ to @@ (according to specification).
-	for k, v := range topLevel {
-		if strings.HasPrefix(k, "@") && !strings.HasPrefix(k, "@@") {
-			topLevel["@"+k] = v
-			delete(topLevel, k)
-		}
-	}
+	// Escape any @ to @@ (according to specification).
+	for k, v := range e.Properties {
+		if strings.HasPrefix(k, "@") && !strings.HasPrefix(k, "@@") {
+			delete(topLevel, k)
+			topLevel["@"+k] = v
+		}
+	}

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: c276ad9f-19b1-4da8-b8e4-4847cdeba15f

📥 Commits

Reviewing files that changed from the base of the PR and between ad56312 and 6b93acc.

📒 Files selected for processing (10)

• .changes/v0.8.1.md
• CHANGELOG.md
• README.md
• event.go
• event_test.go
• flusher.go
• flusher_test.go
• handler.go
• seqotel/seqotel.go
• tool/tester/go.mod

💤 Files with no reviewable changes (1)

• flusher_test.go