feat: Add Kestra orchestrator support

[mingjerli]

Summary

• Add KestraOrchestrator class for generating Kestra YAML flows
• Add to_kestra_flow() method to Pipeline class
• Support cron schedules, custom connection config, and labels
• Generate YAML flows with automatic task dependencies using dependsOn

Changes

New Files

• src/clgraph/orchestrators/kestra.py - KestraOrchestrator class
• tests/test_kestra_integration.py - 24 comprehensive tests

Modified Files

• src/clgraph/orchestrators/__init__.py - Export KestraOrchestrator
• src/clgraph/pipeline.py - Add to_kestra_flow() method

Features

• YAML output - Generates human-readable YAML workflow definitions
• Automatic dependencies - Tasks wired based on table lineage using dependsOn
• Scheduling - Cron schedules via triggers
• Retries - Configurable retry attempts with ISO 8601 duration
• Labels - Custom key-value labels for flow organization

Example

from clgraph import Pipeline

pipeline = Pipeline.from_sql_files("sql/", dialect="clickhouse")

yaml_content = pipeline.to_kestra_flow(
    flow_id="analytics_pipeline",
    namespace="clgraph.production",
    cron="0 6 * * *",
)

with open("flows/analytics.yml", "w") as f:
    f.write(yaml_content)

Test plan

• All 24 tests pass
• Pre-commit checks pass
• Tested with Kestra Docker container

🤖 Generated with Claude Code