Support Ticket System API

Problem/Feature Description

A SaaS company needs a Flask API for their internal support ticket system. Support agents create tickets on behalf of customers, update ticket status, and add comments.

Data model:

• Ticket: title, description, status (open/in_progress/resolved/closed), priority (low/medium/high/urgent), customer_email, created_at, updated_at
• Comment: text, author_name, created_at (per ticket)

Endpoints:

• POST /api/tickets -- create a ticket (title, description, customer_email, priority required)
• GET /api/tickets -- list tickets with optional ?status=open&priority=urgent filters
• GET /api/tickets/<id> -- get ticket with its comments
• PATCH /api/tickets/<id> -- update status and/or priority
• POST /api/tickets/<id>/comments -- add a comment to a ticket
• GET /api/health -- health check endpoint returning {"status": "healthy"}

Requirements:

• Status transitions must be validated: a "closed" ticket cannot be reopened (PATCH should return an error).
• Customer email must be a valid email format.
• All responses (success and error) must follow a consistent JSON structure.
• Logging: every request should be logged with method, path, status code, and duration.
• The app must handle both JSON content type requests and return proper errors for non-JSON POST/PATCH requests.
• Configuration should support different environments (development, testing, production).

Output Specification

Produce Python source files in a ticket-system/ directory:

• app/__init__.py -- application factory
• app/extensions.py -- extension instances
• app/errors.py -- custom exceptions and error handlers
• app/db.py -- data store
• app/routes/tickets.py -- tickets blueprint
• app/routes/comments.py -- comments blueprint
• app/routes/health.py -- health blueprint
• config.py -- configuration classes (Development, Testing, Production)
• tests/conftest.py -- test fixtures
• run.py -- entry point
• requirements.txt

Do not run pip install or start the server.