Support activity feed embedding and add support for web hooks

[arulataequalis]

We heavily rely on codestream for code reviews which is awesome. I personally advocate it to my team and management. It's a great tool. With few more additions it will look even greater. Currently we could see the activity feed only in the IDE. We have a need to ensure that every branch is reviewed at least by two people. There is no way to ensure it now. We use screenshots. Instead if codestream activity can be embedded automatically to a GitLab MR, a Jira Ticket it would be a good addition to the workflow.

Also in addition to slack, having the notification sent to discord would also be good thing to have.