class HaveAPI::Validators::Numericality

Checks the value is a number or a string containing only digits.

Full form:

string :param, number: {
  min: 3,
  max: 10,
  step: 2,
  message: 'the error message'
}

Will allow values ‘3`, `5`, `7` and `9`.

string :param, number: {
  min: 3,
  max: 10,
  mod: 2,
}

Will allow values ‘4`, `6`, `8` and `10`.