Added "Return" parameter to Query. (#1199)

* Added "Return" parameter to Query.

* Fixed api naming by JRediSearch, aslo added LimitKeys method

src/NRediSearch/Query.cs

@@ -143,6 +143,8 @@ public Paging(int offset, int count)
         /// </summary>
         public string Language { get; set; }
         internal string[] _fields = null;
+        internal string[] _keys = null;
+        internal string[] _returnFields = null;
         /// <summary>
         /// Set the query payload to be evaluated by the scoring function
         /// </summary>
@@ -210,6 +212,18 @@ internal void SerializeRedisArgs(List<object> args)
                 args.Add(_fields.Length.Boxed());
                 args.AddRange(_fields);
             }
+            if (_keys?.Length > 0)
+            {
+                args.Add("INKEYS".Literal());
+                args.Add(_keys.Length.Boxed());
+                args.AddRange(_keys);
+            }
+            if (_returnFields?.Length > 0)
+            {
+                args.Add("RETURN".Literal());
+                args.Add(_returnFields.Length.Boxed());
+                args.AddRange(_returnFields);
+            }
 
             if (SortBy != null)
             {
@@ -323,6 +337,28 @@ public Query LimitFields(params string[] fields)
             return this;
         }
 
+        /// <summary>
+        /// Limit the query to results that are limited to a specific set of keys
+        /// </summary>
+        /// <param name="fields">fields a list of TEXT fields in the schemas</param>
+        /// <returns>the query object itself</returns>
+        public Query LimitKeys(params string[] keys)
+        {
+            _keys = keys;
+            return this;
+        }
+
+        /// <summary>
+        /// Result's projection - the fields to return by the query
+        /// </summary>
+        /// <param name="fields">fields a list of TEXT fields in the schemas</param>
+        /// <returns>the query object itself</returns>
+        public Query ReturnFields(params string[] fields)
+        {
+            _returnFields = fields;
+            return this;
+        }
+
         public readonly struct HighlightTags
         {
             public HighlightTags(string open, string close)