Move isExpired from SimpleJWS to JWS

[chalasr]

I propose this change in order to be able to check if a JWS created from an instance of Namshi\JOSE\JWS is expired or not (and not only from SimpleJWS), sort as we can do the check even if using the SecLib encryption engine.

Or is there something in the method that is not directly compatible with the JWS class, or that doesn't make sense to exist into?
ATM I need to duplicate the isExpired method in my project to do this chek on Namshi\JOSE\JWS instances.

[odino]

hey @chalasr, thanks for this :) why not using the SimpleJWS class rather than JWS? We created SimpleJWS to add convenient methods on top of the bare JWS implementation, that was the original idea on why those methods were there.

[chalasr]

Hi @odino
In fact, the SimpleJWS class seems to be only for OpenSSL, rightt?
Because SimpleJWS doesn't take an encryption engine as constructor arg.
I need to use the SecLib and your doc sounds like that we have to use the JWS class.
So maybe, rather than move the method, I can make the SimpleJWS class working for SecLib?

[odino]

@chalasr definitely! Im not sure why it shouldnt be working with seclib but I think the best solution here is to make it working regardless of the underlying sec implementation

Closing this for now, waiting for a PR :)

Thanks man!