User login

{
  "form": {
    "id": "1uap1w5",
    "valid": false,
    "posted": false,
    "errors": {},
    "data": {
      "username": "",
      "password": ""
    },
    "constraints": {
      "username": {
        "minlength": 4,
        "required": true
      },
      "password": {
        "minlength": 6,
        "required": true
      }
    }
  }
}