Add support for random file naming flag

[ianjasperlean]

Hi just want to propose some minor changes if you can support uuid naming out of the box when uploading a file?
For example:
@post('upload')
@UseInterceptors(
GCloudStorageFileInterceptor('file', {
randomFilename: true
}),
)
uploadFile(@uploadedfile() file: UploadedFileMetadata) {
console.log(file);
}

You may want to store the file with an arbitrary name instead of the original file name. You can do this by passing the randomFilename property attribute set to true as follows: