Get the next available posting time slot

{  "$schema": "https://example.com/api/v1/schemas/NextAvailableSlotOutputBody.json",  "message": "string",  "slot": {    "$schema": "https://example.com/api/v1/schemas/PostingScheduleResponse.json",    "created_at": "string",    "day_of_week": 0,    "id": "string",    "is_active": true,    "label": "string",    "local_day_of_week": 0,    "local_hour": 0,    "local_minute": 0,    "utc_hour": 0,    "utc_minute": 0,    "workspace_id": "string"  },  "slot_time": "string"}