maxLength (value, schema, opts) {
    return maxLengthCommon('maxLength', value, schema, opts)
  }
Validates the length of the provided string against a maximum value defined in the Schema's `maxLength` keyword.
Validation succeeds if the length of the string is less than, or equal to the value of this keyword.
see http://json-schema.org/latest/json-schema-validation.html#anchor26

@name Schema.validationKeywords.maxLength
@method
@param {*} value String to be validated.
@param {object} schema Schema containing the `maxLength` keyword.
@param {object} [opts] Configuration options.
@returns {(array|undefined)} Array of errors or `undefined` if valid.