Support posting JSON to generic webhooks

[paulfwilliams]

My company uses RingCentral (the Glip application) for messaging. RingCentral supports incoming messaging hooks from several different applications. We have some apps (Jenkins build, for example) hooked up with notifications already.

I am currently adding Watchtower support for some containers we need updated frequently. I would like to be able to send notifications from Watchtower to the RingCentral Glip application, so my developer group knows when containers have been updated.

RingCentral exposes a generic webhook interface with a definition like:

POST https://hooks.glip.com/webhook/...144 character base 64 encoded identifier...
Content-Type: application/json

{
"activity": "Watchtower Notification",
"iconUri": "https://containrrr.dev/watchtower/images/logo-450px.png",
"title": "post title",
"text": "post text"
}

It would be great if Watchtower would be able to call this webhook with a JSON object that I specify. For example:

--notification: webhook
--notification-url: "https://hooks.glip.com/webhook/...144 character base 64 encoded identifier..."
--notification-template: "{"activity": ...custom JSON... }"

Alternatively, there are implementations for specific applications in Glip. That would be great, too, but a generic webhook seems more widely applicable. See this URL for more information about RingCentral integration: https://developers.ringcentral.com/guide/team-messaging/manual/webhook-posting