Feature Request - Web Hooks

[stuartm]

Please forgive me if you're not accepting feature requests through Issues, I couldn't find any mention of your feature request policy.

It would be great if Staytus was able to call user-configured APIs on certain trigger events such as a change of Service Status, Issue Updates, Start/End of maintenance.

The particular use case I have in mind is posting updates to a Mattermost Channel. A generic enough implementation would allow for integration with a wide variety of different services from other chat platforms Slack/Hipchat to enabling automated calls, SMS messages and much more.