Add configurable notifications with Slack webhook support

[Copilot]

Implements comprehensive notification system supporting both traditional webhooks and Slack webhooks with configurable triggers for job start and completion events.

New Features

Slack Webhook Support

• Rich formatted notifications with status-specific colors (green for success, red for failure, blue for cancellation)
• Job details including command, timing information, and PID
• Direct links to job logs, results, and status pages
• Configurable for start and/or completion events

Enhanced Job Submission

Added optional notification parameters:

• slack_webhook: Slack webhook URL for rich notifications
• notify_on_start: Enable notifications when jobs begin execution
• notify_on_finish: Enable notifications when jobs complete

Backward Compatibility

• Traditional webhook parameter continues to work unchanged
• Enhanced traditional webhook payload now includes log_url
• Both notification types can be used simultaneously

Usage Examples

Slack notifications only:

{
  "args": ["python", "process_data.py"],
  "slack_webhook": "https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK",
  "notify_on_start": true,
  "notify_on_finish": true
}

Both notification types:

{
  "args": ["backup_database.sh"],
  "webhook": "https://your-system.com/webhook",
  "slack_webhook": "https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK",
  "notify_on_finish": true
}

The implementation preserves all existing functionality while adding powerful new notification capabilities for better job monitoring and team collaboration.

Fixes #1.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• hooks.slack.com
  • Triggering command: ./processjobqueue (dns block)
• webhook.site
  • Triggering command: ./processjobqueue (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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[Copilot]

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