Add download stop API for download service

[namchuai]

Describe Your Changes

• Refactor to add download stop API.
• Using multi interface from libcurl.
• Throttle event by 1 sec
• Return DownloadTask when calling download API.

API:

curl --location --request DELETE 'http://127.0.0.1:39281/models/pull' \
--header 'Content-Type: application/json' \
--data '{
    "taskId": <your_download_task_id>
}'

Response when calling Download API

{
    "message": "Model start downloading!",
    "task": {
        "id": "Mistral-7B-Instruct-v0.1-GGUF",
        "items": [
            {
                "bytes": 3822024352,
                "checksum": "N/A",
                "downloadUrl": "https://huggingface.co/TheBloke/Mistral-7B-Instruct-v0.1-GGUF/resolve/main/mistral-7b-instruct-v0.1.Q3_K_L.gguf",
                "downloadedBytes": 0,
                "id": "TheBloke:Mistral-7B-Instruct-v0.1-GGUF:mistral-7b-instruct-v0.1.Q3_K_L.gguf",
                "localPath": "/Users/jamesnguyen/cortexcpp/models/huggingface.co/TheBloke/Mistral-7B-Instruct-v0.1-GGUF/mistral-7b-instruct-v0.1.Q3_K_L.gguf"
            }
        ],
        "type": "Model"
    }
}

Issue

• Fix idea: [DownloadEvent] Adding download stop API #1398
• Fixes feat: Model Pull has clear API and CLI to support Huggingface Repos #1242

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[dan-menlo]

@namchuai At the conclusion of this issue, please make sure we add this to the API Reference (i.e. swagger). cc @gabrielle-ong

[vansangpfiev]

Great work!

[gabrielle-ong]

@namchuai can I check if this new endpoint DELETE models/pull is added to Swagger?