Add a validation for time based attribute

[jwoertink]

I think it would be awesome to have a time based validator where you could say

validate_time cc_exp_date, after: 1.day.from_now

validate_time expired_at, before: 1.year.from_now

[skojin]

rails recently solved this with ComparisonValidator https://www.bigbinary.com/blog/rails-7-adds-comparison-validator-to-active-record