Improve the payload in the `metadata` field of `FileUploadedEvent` in the Local provider

[javiertoledo]

1. There's a mismatch in the name of the field that contains the file name. The README file shows fileName, but the code is currently injecting this field as just name
2. It could be convenient to include the directory name in addition to the filename to be able to easily reconstruct the path when reading the event. It would also be nice if the event class had a helper method to build and return the path to the file instead of having to manually build it.