[6.x] Split hasValidSignature method

[dwightwatson]

This splits up the functionality of the hasValidSignature method into two separate checks - whether the signature matches the given path/URL, and whether the expires timestamp has since passed or not.

The benefit of providing access to these separately is it allows apps to handle these cases differently. It would allow you to catch InvalidSignatureException and then provide a better user experience when a signature was actually correct, but has just since expired.

My use case is that some emails we send include signed URLs that will automatically log our users in and then redirect them to the page the user intended to go to. In the case that the URL has expired I would still like redirect them to the intended page, but just skip the automatic login.

[netpok]

Maybe we should introduce an ExpiredSinatureException which extends the InvalidSignatureException?

[dwightwatson]

@netpok I was actually ready to put a PR together that was exactly like that, but felt that implementation may have been a little too heavy. This PR was a simpler compromise.

https://github.com/laravel/framework/compare/6.x...dwightwatson:signature-expiry?expand=1

[ghost]

Could you do this PR?