Don't strip trailing slash if it's escaped in StripSlashes middlware

[nuuls]

This fixes an edge case where a path ending in a trailing encoded slash %2F is incorrectly stripped and rctx.RoutePath is set to the unescaped Path, resulting in routing errors.

The specific edge case in my project is:

• rctx is nil
• rctx.RoutePath is empty
• r.URL.RawPath contains multiple escaped slashes in various places
• rctx.RoutePath is set to the unescaped values contained in r.URL.Path
• The Mux no longer matches the route /link_resolver/{url} because all %2F are now /

A similar issue also exists in RedirectSlashes, I can open a second PR for that as well if you'd like.

[VojtechVitek]

LGTM

Can you please force-push to the branch to kick off CI?

[brasic]

@VojtechVitek it seems like the author may have abandoned this PR, but it's needed: the current behavior strips trailing %2F strings from the URL inappropriately. I've tested this code in our project and it fixed the issue. If @nuuls isn't around to kick-off CI I'm happy to open a new PR with this content to do so.

Although this might properly be considered a breaking change since in my experience it changes the routing of plenty of real-world URLs that apps might have depended on.

[nuuls]

Ah sorry, completely forgot about this one 😄 Pushed it now