Get a project variable

curl --request GET \
  --url {schemes}://api.upsun.com/projects/{projectId}/variables/{projectVariableId} \
  --header 'Authorization: Bearer <token>'

{
  "id": "<string>",
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "name": "<string>",
  "attributes": {},
  "is_json": true,
  "is_sensitive": true,
  "visible_build": true,
  "visible_runtime": true,
  "application_scope": [
    "<string>"
  ],
  "value": "<string>"
}