fix after test

src/main/java/ru/soune/nocopy/dto/file/FileExtensionResponse.java

@@ -0,0 +1,17 @@
+package ru.soune.nocopy.dto.file;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.Builder;
+import lombok.Data;
+
+import java.util.List;
+
+@Data
+@Builder
+public class FileExtensionResponse {
+    @JsonProperty("file_extension")
+    private List<String> extension;
+
+    @JsonProperty("count")
+    private Integer count;
+}