Add real-time notifications for refresh job statuses

[niteshpurohit]

Feature Request

Description:

Add a notification system to alert external services about the status of refresh jobs, particularly failures. This could be implemented via webhooks, email, or Slack notifications.

Use Case:

Provides immediate feedback to operations teams when a critical refresh job fails, enabling a faster response than periodically checking a dashboard.

Proposed Solution:

• Allow notification endpoints (webhook URL, email address) to be configured in the initializer or on the view definition itself.
• After MatViewRefreshJob completes (on success or failure), trigger a notification with a payload containing the view name, status, and error details.

RSpec Tests:

• Configure a webhook endpoint in the tests.
• Trigger a successful job and a failed job.
• Verify that a POST request with the correct payload is sent to the webhook endpoint in both cases.
• Test that no notification is sent if one is not configured.

Checklist:

• I have searched for a similar feature request and didn't find any duplicates.
• I have included all the required information.
• I have tagged the issue with the label "enhancement".

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