feat(trigger): implement complete OAuth authorization flow for trigger providers

- Add OAuth authorization URL generation API endpoint
- Implement OAuth callback handler for credential storage
- Support both system-level and tenant-level OAuth clients
- Add trigger provider credential encryption utilities
- Refactor trigger entities into separate modules
- Update trigger provider service with OAuth client management
- Add credential cache for trigger providers

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

api/services/trigger_service.py

@@ -1,5 +1,4 @@
 import logging
-from typing import Any
 
 from flask import Request, Response
 
@@ -21,3 +20,4 @@ class TriggerService:
         # TODO dispatch by the trigger controller
 
         # TODO using the dispatch result(events) to invoke the trigger events
+        raise NotImplementedError("Not implemented")