Event based webhooks

[bmc-msft]

This PR adds support for arbitrary third-party integrations via webhooks, modeled after Github Webhooks.

Users will be able to specify URL that OneFuzz will call and a set of events that will hit said URL.

Currently, the event types supported are:

• task_created (sends a WebhookEventTaskCreated)
• task_stopped (sends a WebhookEventTaskStopped)
• task_failed (sends a WebhookEventTaskFailed)

The webhooks will atempt up to 5 times, then be marked as failed.

Features:

• onefuzz webhook logs UUID retrieves a log of all of the messages sent to the webhook for the last 7 days.
• onefuzz webhook ping UUID sends a special webhook with a generated GUID to verify the webhooks are setup.
• Webhook logs are automatically removed after 7 days.
• Webhook schema (using openapi spec) have documentation & example payloads provided via code generation. (CI verifies that said documentation is up-to-date).
• Messages sent to a webhook can optionally be verified using HMAC-SHA512.

[bmc-msft]

Until this is merged, this link should work to view the generated webhook documentation.

https://github.com/bmc-msft/onefuzz/blob/event-based-webhooks/docs/webhook_events.md

[ghost]

Hello @bmc-msft!

Because this pull request has the auto-merge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[ghost]

Apologies, while this PR appears ready to be merged, it looks like main is a protected branch and I have not been granted permission to perform the merge.