Allow to access uri of QueryStringDecoder. Related to [#2896]

Motivation:

Sometimes it is useful to be able to access the uri that was used to initialize the QueryStringDecoder.

Modifications:

Add method which allows to retrieve the uri.

Result:

Allow to retrieve the uri that was used to create the QueryStringDecoder.

codec-http/src/main/java/io/netty/handler/codec/http/QueryStringDecoder.java

@@ -165,6 +165,13 @@ public class QueryStringDecoder {
         this.maxParams = maxParams;
     }
 
+    /**
+     * Returns the uri used to initialize this {@link QueryStringDecoder}.
+     */
+    public String uri() {
+        return uri;
+    }
+
     /**
      * Returns the decoded path string of the URI.
      */