fix: add response documentation

Author: daniel-kmiecik

modules/swagger-generator/src/main/java/io/swagger/generator/resource/SwaggerResource.java

@@ -3,6 +3,8 @@
 import io.swagger.annotations.Api;
 import io.swagger.annotations.ApiOperation;
 import io.swagger.annotations.ApiParam;
+import io.swagger.annotations.ApiResponse;
+import io.swagger.annotations.ApiResponses;
 import io.swagger.codegen.CliOption;
 import io.swagger.codegen.Codegen;
 import io.swagger.codegen.CodegenConfig;
@@ -69,6 +71,11 @@ public class SwaggerResource {
             notes = "A valid `fileId` is generated by the `/clients/{language}` or `/servers/{language}` POST "
                     + "operations.  The fileId code can be used just once, after which a new `fileId` will need to "
                     + "be requested.", response = String.class, tags = {"clients", "servers"})
+    @ApiResponses(value = {
+            @ApiResponse(code = 200, message = "File successfully downloaded. Response contains ZIP file bytes."),
+            @ApiResponse(code = 404, message = "File with the given fileId not found or already downloaded."),
+            @ApiResponse(code = 500, message = "Server error while reading or returning the file.")
+    })
     public Response downloadFile(@PathParam("fileId") String fileId) {
         Generated g = fileMap.get(fileId);
         LOGGER.info("Looking for fileId: {}", fileId);