Feature Request: Add Activity Hooks and Webhooks for Attachment Events

[thuanpham582002]

Problem

Currently, BookStack does not have activity hooks or webhooks for attachment-related events. This makes it impossible to integrate external services (like AI processing, backup systems, or notification services) when attachments are uploaded, updated, or deleted.

Use Cases

1. AI Processing: Automatically process uploaded documents (e.g., extract content from PDFs, generate summaries)
2. Backup Systems: Trigger backups when files are uploaded or modified
3. External Notifications: Notify Slack/Discord when files are uploaded
4. Audit Logging: Track all file uploads/downloads for compliance

Current Workaround

The only available workaround is to monitor page_update events and parse HTML content for attachment links, which is unreliable and indirect.

Proposed Solution

Add three new activity types and webhooks:

1. attachment_create - Triggered when a file is uploaded to a page
2. attachment_update - Triggered when an attachment is updated/replaced
3. attachment_delete - Triggered when an attachment is deleted

Implementation Approach

Add constants to ActivityType.php:

const ATTACHMENT_CREATE = 'attachment_create';
const ATTACHMENT_UPDATE = 'attachment_update';
const ATTACHMENT_DELETE = 'attachment_delete';

Add activity logging in AttachmentService.php:

// In saveNewUpload()
Activity::add(ActivityType::ATTACHMENT_CREATE, $attachment);

// In saveUpdatedUpload()
Activity::add(ActivityType::ATTACHMENT_UPDATE, $attachment);

// In deleteFile()
Activity::add(ActivityType::ATTACHMENT_DELETE, $attachment);

Webhook Payload Example

{
  "event": "attachment_create",
  "text": "Admin uploaded attachment \"document.pdf\"",
  "triggered_by": {
    "id": 1,
    "name": "Admin"
  },
  "related_item": {
    "id": 5,
    "name": "document.pdf",
    "extension": "pdf",
    "page_id": 123,
    "external": false
  }
}

Impact

• Low breaking change risk: Only adds new events, existing functionality unaffected
• Backward compatible: Existing webhooks continue to work
• Theme hooks compatible: Users can also use Theme::listen(ThemeEvents::ACTIVITY_LOGGED) and filter by the new event types

Priority

Medium - This is a common enterprise requirement for document management systems.

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Is this something the maintainers would consider? I'd be willing to contribute a PR if this is desired.