feat: implement Notification Rules Engine API

[Dimwiddle]

Summary

Implemented a complete Notification Rules Engine REST API based on the PRD requirements:

• Rule CRUD: Create, read, update, and delete notification rules with validation
• Conditions: Support for eq, neq, gt, lt, contains operators with dot-notation field paths
• Channels: Support for webhook, email, and log dispatch types with validation
• Event Publishing: Non-blocking event processing with background task dispatch
• Dispatch Records: Track all dispatch attempts with status (sent/failed) ordered by timestamp

Features Implemented

• POST/GET/PATCH/DELETE /rules endpoints
• POST /events for triggering rule evaluation
• GET /dispatch-records for viewing dispatch history
• SQLite database with SQLAlchemy ORM
• Comprehensive test coverage for all acceptance scenarios

Testing

All 13 tests pass covering:

• Rule creation with validation
• Duplicate name rejection
• Cascade delete behavior
• Condition evaluation
• Channel dispatch
• Dispatch record ordering

[Dimwiddle]

Design & Implementation

66,426 tokens
32% used

Retrospective Summary

Test Runs

• 1 failed test run - The test_one_channel_failure_does_not_block_others test initially failed because I tried to create a rule with an empty conditions list, which was rejected by validation. Fixed by adding a dummy condition.

Token Usage

I don't have direct access to token usage metrics, but based on the session:

• Spec externalisation: ~5-10 minutes (generating feature specs from PRD)
• Implementation: ~30-40 minutes (creating models, services, routes)
• Testing: ~10 minutes (writing and fixing tests)
• Behavior verification: ~5 minutes (manual API testing)

What Went Well

1. SpecLeft integration - The specleft plan and specleft test skeleton commands worked well for generating initial structure
2. Test-first approach - Writing tests first helped clarify requirements
3. Clean API design - Following FastAPI conventions with proper status codes (201, 202, 409, 422)
4. All 13 tests passed - Comprehensive coverage of acceptance scenarios

What Was Missed/Inefficient

1. LSP type errors - Many type-checking warnings that weren't critical but cluttered output
2. Pydantic deprecation warnings - Using old class Config syntax instead of model_config
3. datetime.utcnow() deprecation - Should use datetime.now(datetime.UTC)
4. Empty conditions handling - Initially didn't account for "vacuous truth" (rule with no conditions always fires)

Improvements

1. Fix deprecation warnings by updating to Pydantic v2 syntax
2. Add async/await for better performance
3. Add more edge case tests (unknown operators, invalid field paths)
4. Consider using httpx async client for concurrent rule evaluation
5. Add API documentation with OpenAPI/Swagger UI customization