Feature: Implement Subtask Management for TickTick Tasks

[krisrowe]

The TickTick API supports subtasks (referred to as 'items') within a parent task, as observed in the response from the endpoint. Our current tools do not expose functionality to manage these subtasks.

API Response Example showing Subtasks ( array):

{
"tasks": [{
    "id": "6247ee29630c800f064fd145",
    "title": "Task Title",
    "content": "Task Content",
    "items": [{
        "id": "6435074647fd2e6387145f20",
        "status": 0,
        "title": "Subtask Title",
        "sortOrder": 12345,
        "startDate": "2019-11-13T03:00:00+0000",
        "isAllDay": false,
        "timeZone": "America/Los_Angeles",
        "completedTime": "2019-11-13T03:00:00+0000"
    }]
}]
}

Update Task Example with Subtasks ( array and ):

{  
"id" : "63b7bebb91c0a5474805fcd4",  
"projectId" : "6226ff9877acee87727f6bca",  
"title" : "Task Title",  
"content" : "Task Content",  
"desc" : "Task Description",  
"isAllDay" : true,  
"startDate" : "2019-11-13T03:00:00+0000",  
"dueDate" : "2019-11-14T03:00:00+0000",  
"timeZone" : "America/Los_Angeles",  
"reminders" : [ "TRIGGER:P0DT9H0M0S", "TRIGGER:PT0S" ],  
"repeatFlag" : "RRULE:FREQ=DAILY;INTERVAL=1",  
"priority" : 1,  
"status" : 0,  
"completedTime" : "2019-11-13T03:00:00+0000",  
"sortOrder" : 12345,  
"items" : [ {  
    "id" : "6435074647fd2e6387145f20",  
    "status" : 1,  
    "title" : "Item Title",  
    "sortOrder" : 12345,  
    "startDate" : "2019-11-13T03:00:00+0000",  
    "isAllDay" : false,  
    "timeZone" : "America/Los_Angeles",  
    "completedTime" : "2019-11-13T03:00:00+0000"  
    } ], 
"kind": "CHECKLIST"
}

Proposed Changes:
Implement new functions or extend existing ones in to support the following subtask operations:

1. Read Subtasks: Extend or add a new tool to retrieve subtasks associated with a parent task.
2. Create Subtask: Add a new tool to create a subtask under a specified parent task.
3. Update Subtask: Add a new tool to modify an existing subtask.
4. Complete Subtask: Add a new tool to mark a subtask as complete.
5. Delete Subtask: Add a new tool to delete a subtask.

This will involve examining the TickTick OpenAPI specification (if available) or further reverse-engineering the API to determine the correct endpoints and request/response formats for subtask management.