Encoding the file name to Hashed one (something like SHA-1) to void same file name issue

[KagefumiMerry]

Currently the file name could not be the same when upload to Candidate Attachments, it would show this error message: This attachment has already been added to this candidate.

Change the file name to SHA-1 would resolve this issue (In most cases, when attaching emails files, the file name would be the same)

Also, this would make it less issue regarding the file system to avoid file/path name too long or file name encoding issue.