Allow IssuedAtClaim to compare dates

[hhanesand]

I'm using Firebase to manage my users, and I use this library to validate JWT tokens sent by Firebase. In their documentation, they state that I must validate that the Issued-at time is in the past. I don't think I can do this with the current implementation, as IssuedAtClaim forces comparison to a specific time.

[siemensikkema]

I had a look at the jwt spec and in section 4.1.6. it does not say anything about how to verify these claims. I now see the implementation I chose does not fit all needs :(
The good news is that you don't have to use the provided claims. What you need is the opposite of NotBeforeClaim so you could copy and adjust the verify function and the static name variable.

[hhanesand]

Ah, ok. Thanks for the response.

Also, thank you for the work you did here! This allowed me to remove a janky Swift + Ruby system I had set in place :)