static create(req, res) {
    const {
      username,
      email,
      password
    } = req.body;

    models.User.create({
      username: username,
      email: email,
      password: password
    })
      .then(() => {
        res.status(201).json({
          success: true,
          message: "Pomyślnie założono konto."
        });
      })
      .catch(err => {
        res.status(err.errors[0].message.statusCode).json({
          success: false,
          message: err.errors[0].message.errorMessage,
        });
      });
  }