Add support for server-side configurable Webhooks

[jkhoel]

Webhooks are user-defined HTTP POST callbacks. They provide a lightweight mechanism for letting remote applications receive push notifications from the backend, without requiring polling. For example, you may want any event updates to be pushed to a Discord channel, or some sort of messaging app.

[jkhoel]

There are apperantly a few ways to go about this:

• Using node-webhooks, a ready-module
• Hard-coding the webhook into each API endpoint function

I think the best way would be to have a global function available that could be inserted into any endpoint we would like to be exposed to webhooks.

[jkhoel]

Implementation like this:

config/webhooks.js:

module.exports = {
  POST_NEW_EVENT: (req) => {
    const { id, name, date } = req.body;
    const url = `www.someService.com/events/new?id=${id}&name=${name}&date=${date}`

    return new Promise((resolve) => {
      HTTPrequestToService(url) // Make the request to the url
      resolve(true)  // or some other result
    })
  },
  SOME_OTHER_HOOK: () => null,
}

route/events.js:

// Import the webhooks config
const webhooks = require('../../config/webhooks');

router.POST('/new', (req, res) => {
  // Trigger a webhook
  webhooks.POST_NEW_EVENT(req);

  // ... do further SQL queries and actual endpoint stuff
});