Retrieve a specific captive portal Instance

curl --request GET \
  --url https://api.altostrat.io/instances/{instance} \
  --header 'Authorization: Bearer <token>'

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "auth_integration_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "strategy": "oauth2",
  "name": "<string>",
  "session_ttl": 123,
  "auth_window_ttl": 123,
  "coupon_ttl": 123,
  "theme": {
    "logo": "<string>",
    "icon": "<string>",
    "accent_text": "<string>",
    "accent_color": "<string>",
    "text_color": "<string>",
    "secondary_text_color": "<string>",
    "background_color": "<string>",
    "border_color": "<string>",
    "box_color": "<string>"
  },
  "terms_text": "<string>",
  "locale": "en",
  "sites": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "subnets": [
        "<string>"
      ]
    }
  ],
  "created_at": "2023-11-07T05:31:56Z",
  "preview_url": "<string>"
}