Fix duplicate keys causing an exception

tests/Jellyfin.Server.Integration.Tests/Controllers/EncoderController.cs

@@ -29,5 +29,25 @@ namespace Jellyfin.Api.Controllers
                 StatusCode = 200
             };
         }
+
+        /// <summary>
+        /// Tests the url decoding.
+        /// </summary>
+        /// <param name="params">Parameters to echo back in the response.</param>
+        /// <returns>An <see cref="OkResult"/>.</returns>
+        /// <response code="200">Information retrieved.</response>
+        [HttpGet("UrlArrayDecode")]
+        [ProducesResponseType(StatusCodes.Status200OK)]
+        public ContentResult TestUrlArrayDecoding([FromQuery] Dictionary<string, string[]>? @params = null)
+        {
+            return new ContentResult()
+            {
+                Content = (@params != null && @params.Count > 0)
+                    ? string.Join("&", @params.Select(x => x.Key + "=" + string.Join(',', x.Value)))
+                    : string.Empty,
+                ContentType = "text/plain; charset=utf-8",
+                StatusCode = 200
+            };
+        }
     }
 }