Build a Task Tracker API

Problem/Feature Description

A development team wants a simple task tracker backend. Build it using Go with the standard library (net/http).

Resources:

• Task: { id, title, description, status, assignee, createdAt, updatedAt }
• Status must be one of: todo, in_progress, done

Endpoints:

• GET /api/tasks -- list all tasks, with optional query parameter ?status=todo to filter
• GET /api/tasks/{id} -- get a single task
• POST /api/tasks -- create a task (title required, status defaults to todo)
• PATCH /api/tasks/{id} -- update task fields (partial update)
• DELETE /api/tasks/{id} -- delete a task
• POST /api/tasks/{id}/assign -- assign a task to someone (body: { "assignee": "alice" })

Use in-memory storage. Generate IDs using a counter or UUID.

Output Specification

Produce:

• main.go -- server entry point
• Source files for handlers, models, and any middleware
• go.mod -- module definition

You may split across additional files as needed.