feat(csharp): implement telemetry tag definitions (phase 1)

[sreekanth-db]

🥞 Stacked PR

Use this link to review incremental changes.

• stack/telemetry-phase-1 [Files changed]
  • stack/telemetry-phase-2.0 [Files changed]

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What's Changed

This PR implements Phase 1 of telemetry tag definitions (telemetry-activity-based-design.md) for the C# Databricks ADBC driver, establishing structured telemetry collection with privacy-aware export controls.

Changes

Introduces a declarative tag definition system across three telemetry event types:

1. Connection Events - Captures connection lifecycle and driver configuration

• Identity: workspace ID, session ID
• Driver metadata: version, OS, .NET runtime
• Feature flags: CloudFetch, LZ4, direct results, multiple catalog, trace propagation
• Local-only: server addresses

2. Statement Execution Events - Tracks query performance and resource usage

• Result metrics: format, chunk count, bytes downloaded, row count
• Polling metrics: poll count, latency
• Operation metadata: operation type (SELECT, INSERT, etc.)
• Local-only: SQL text, catalog/schema names

3. Error Events - Records error patterns and retry behavior

• Classification: error type, HTTP status codes, SQL states
• Retry context: retry count, operation context
• Local-only: error messages, stack traces

Export Scope Design

Tags use TagExportScope enum to control export destinations:

• ExportLocal - Sensitive data only (SQL, errors, addresses)
• ExportDatabricks - Only to databricks service
• ExportAll - Non-sensitive operational metrics (both local & Databricks)

TelemetryTagRegistry provides centralized privacy filtering via GetDatabricksExportTags() and ShouldExportToDatabricks().

Design Note: Added TODO comment acknowledging the current approach duplicates export scope between attributes and whitelist methods.

Testing

• ✅ All 7 unit tests pass (TelemetryTagRegistryTests)
• ✅ Privacy filters validated (sensitive tags excluded from Databricks export)
• ✅ Unknown event types handled gracefully

Next Steps

Future phases will add ActivityListener, metrics aggregator, and exporter components.

[eric-wang-1990]

Should we log all the property for openConnection? Like query tag, etc?
Does other driver output those properties, any PII info?