feat(connectors): add Apache Airflow trigger sink

[avirajkhare00]

Summary

• Add iggy_connector_airflow_sink that triggers Airflow DAG runs (POST /api/v1/dags/{dag_id}/dagRuns) from Iggy messages
• Support auth modes none / basic / bearer, optional per-message dag_id header override, and nested conf.iggy metadata
• Treat HTTP 409 as success for deterministic dag_run_id redelivery; permanent 4xx drop without retry
• WireMock integration test plus example config / README; tracked by feat(connectors): add Apache Airflow trigger connector #3715

Test plan

• cargo fmt --all
• cargo sort --no-format --workspace
• cargo clippy -p iggy_connector_airflow_sink --all-targets -- -D warnings
• cargo test -p iggy_connector_airflow_sink (11 unit tests)
• cargo test -p integration -- connectors::airflow with WireMock (Docker)
• Local e2e against real Airflow 2.10.5 standalone in Docker (3 DAG runs created)

[github-actions]

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

Slash commands (own line, regular comment) move it around the queue:

• /ready - back to S-waiting-on-review after addressing feedback
• /author - flip to S-waiting-on-author while you finish changes
• /request-review @user-or-team - request a reviewer

See CONTRIBUTING.md for details.

[codecov]

Codecov Report

❌ Patch coverage is 76.77165% with 118 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.31%. Comparing base (4a6f173) to head (daa2ec6).

Files with missing lines	Patch %	Lines
core/connectors/sinks/airflow_sink/src/lib.rs	76.77%	106 Missing and 12 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3716       +/-   ##
=============================================
- Coverage     74.31%   41.31%   -33.01%     
  Complexity      937      937               
=============================================
  Files          1303     1302        -1     
  Lines        148600   129447    -19153     
  Branches     124041   104963    -19078     
=============================================
- Hits         110427    53475    -56952     
- Misses        34705    73136    +38431     
+ Partials       3468     2836      -632     

Components	Coverage Δ
Rust Core	33.56% <76.77%> (-41.01%)	⬇️
Java SDK	62.44% <ø> (ø)
C# SDK	71.05% <ø> (-1.14%)	⬇️
Python SDK	92.15% <ø> (ø)
PHP SDK	84.29% <ø> (ø)
Node SDK	92.49% <ø> (-0.02%)	⬇️
Go SDK	42.87% <ø> (ø)

Files with missing lines	Coverage Δ
core/connectors/sinks/airflow_sink/src/lib.rs	76.77% <76.77%> (ø)

... and 435 files with indirect coverage changes

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