ref: have NewGoKitHandler() return slog.Handler interface type

We still return the concrete implementation in the actual return call,
but the signature should ensure better compatibility with slog.

Signed-off-by: TJ Hoplock <[email protected]>

handler.go

@@ -25,7 +25,7 @@ type GoKitHandler struct {
 // logger. Calls to the slog logger are chained to the handler's internal
 // go-kit logger. If provided a level, it will be used to filter log events in
 // the handler's Enabled() method.
-func NewGoKitHandler(logger log.Logger, level slog.Leveler) GoKitHandler {
+func NewGoKitHandler(logger log.Logger, level slog.Leveler) slog.Handler {
 	if logger == nil {
 		logger = defaultGoKitLogger
 	}