Get add-ons

curl --request GET \
  --url {schemes}://api.upsun.com/organizations/{organization_id}/addons \
  --header 'Authorization: Bearer <token>'

{
  "available": {
    "user_management": {},
    "support_level": {}
  },
  "current": {
    "user_management": {},
    "support_level": {}
  },
  "upgrades_available": {
    "user_management": [
      "<string>"
    ],
    "support_level": [
      "<string>"
    ]
  }
}