[Feature] Webhooks support

未确定任何文件、测试或入口点。请审查提议的元数据和按项目配置的 webhook，然后使用链接的 KernelCI 集成上下文，与维护者明确事件集、身份验证和交付行为；完成的标准应是已就发布所请求的补丁或补丁系列元数据达成一致的设计。

As part of the effort to enhance Kernel testing I am working with KernelCI to implement Patchwork support on their end (kernelci/kernelci-api#307). To make it happen I'd like to propose webhook feature for Patchwork, which will allow us to enable testing patches on KernelCI infrastructure and publish results and Patchwork checks.

I'd like to add webhook logic that will POST patch/series-related metadata [1] into specified URL from per-project webhook config [2]. Config will specify destination tree and branch, and events that should trigger the webhook.

[1] Example metadata

{
  "event": "patch-created",
  "revision": {
    "tree": "mainline",
    "url": "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git",
    "branch": "master"
  },
  "submitter": {
        "id": 1,
        "url": "<URL>",
        "name": "John Doe",
        "email": "example@example.com"
  },
  "patches": [
    {
      "id": 1,
      "hash": "<HASH>",
      "web_url": "<URL>",
      "date": "2023-07-25T05:12:34.478Z",
      "mbox": "<URL>"
    }
  ]
}

[2] Example config

{
  "webhook": {
    "url": "<URL>",
    "auth": {
      "bearer_token": "<TOKEN>"
    }
  },
  "revision": {
    "tree": "mainline",
    "url": "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git",
    "branch": "master"
  },
  "events": [
    "patch-created"
  ]
}

This is not finalized design and I am open to tweak any part of it to fit your requirements. Please let me know what you guys think. Thanks!