Discourse "User Activated" webhook

Fires a user_activated webhook when a user is activated.

Note: This will not fire when a user changes and confirms their email address if they are already active.

Headers include:

X-Discourse-Event-Type: user
X-Discourse-Event: user_activated

Body is the full User event payload:

{
  "user": {
    "id": 1,
    "username": "wilson29thid",
    "email": "[email protected]",
    // etc.
  }
}

Big thanks to @erickguan's custom webhooks tutorial.