Prevent double decoding of % in url params

There was an unfortunate regression in #14293 which has led to the double decoding
of url parameter elements if they contain a '%'. This is due to an issue
with the way chi decodes its RoutePath. In detail the problem lies in
mux.go where the routeHTTP path uses the URL.RawPath or even the
URL.Path instead of the escaped path to do routing.

This PR simply forcibly sets the routePath to that of the EscapedPath.

Fix #17938

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/context/context.go

@@ -609,6 +609,10 @@ func Contexter() func(next http.Handler) http.Handler {
 			var locale = middleware.Locale(resp, req)
 			var startTime = time.Now()
 			var link = setting.AppSubURL + strings.TrimSuffix(req.URL.EscapedPath(), "/")
+
+			chiCtx := chi.RouteContext(req.Context())
+			chiCtx.RoutePath = req.URL.EscapedPath()
+
 			var ctx = Context{
 				Resp:    NewResponse(resp),
 				Cache:   mc.GetCache(),