ISO8601 parser: require the input to be a string
ISO8601 parser: require the input to be a string

The fix for https://www.ruby-lang.org/en/news/2021/11/15/date-parsing-method-regexp-dos-cve-2021-41817/
adds keyword arguments to Date.parse, which in certain Ruby versions means that
attempting to parse a hash will be treated as keyword arguments rather than an
invalid object to parse.

iknow/iknow_params