Fix trailing slash in nested path

This commit adds a trailing slash to the nested path if the request path
also ends with a slash. For instance, given the request "/foo/bar/", and
nested path pattern "/foo/**", we expect the nested path to be “/bar/”,
not “/bar".

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RequestPredicates.java

@@ -386,6 +386,9 @@ public abstract class RequestPredicates {
 			if (!subPath.startsWith("/")) {
 				subPath = "/" + subPath;
 			}
+			if (requestPath.endsWith("/") && !subPath.endsWith("/")) {
+				subPath += "/";
+			}
 			return new SubPathServerRequestWrapper(request, subPath);
 		}