Creates a severity

curl --request POST \
  --url https://api.rootly.com/v1/severities \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '{
  "data": {
    "type": "severities",
    "attributes": {
      "name": "<string>",
      "description": "<string>",
      "severity": "critical",
      "color": "<string>",
      "position": 123,
      "notify_emails": [
        "<string>"
      ],
      "slack_channels": [
        {
          "id": "<string>",
          "name": "<string>"
        }
      ],
      "slack_aliases": [
        {
          "id": "<string>",
          "name": "<string>"
        }
      ]
    }
  }
}'

{
  "data": {
    "id": "879da926-88a5-4666-a440-52280cc8dfc4",
    "type": "severities",
    "attributes": {
      "name": "P0",
      "slug": "p0",
      "description": "High Priority",
      "severity": "medium",
      "color": "#E58A1F",
      "position": 1,
      "notify_emails": [
        "hello@rootly.com",
        "world@rootly.com"
      ],
      "slack_channels": [
        {
          "id": "C03MKDSEJE8",
          "name": "elastisearch"
        }
      ],
      "slack_aliases": [
        {
          "id": "S03F7QUV7F1",
          "name": "leadership"
        }
      ],
      "created_at": "2025-07-11T12:30:52.259-07:00",
      "updated_at": "2025-07-11T12:30:52.259-07:00"
    }
  }
}