Modifying vb3 attachment merge module so that upon transfer of attachments it generates a sha2-256 filehash and stores it in the attachments table in a new column filehash.  The naming of the attachments was also modified to generate a sha2-256 hash of a random string in place of the sha1 of the file per feedback from the MyBB developers on why they originally took the path of hashing a random string for security.
Modifying vb3 attachment merge module to fix the filehash generation so it only does it if the target file exists.  Also setting a default value on the filehash column
Merge branch 'release/vb3-attachments-filehash' into develop