bc: Delete md5 hashing from restore SP 0.5

[Stezido]

Discussed in #870

^{Originally posted by georgimld December 16, 2020}

Summary 💡

When creating a backup, a hashing is now calculated with a sha256 hash. It used to be created with md5, but as mentioned in #513 it wasn't working perfectly. Restoring a backup is now possible with both the old version (md5 hash) and the new (sha256), as implemented in #693 .
Deleting the md5 hash function would not allow old backups to be restored anymore, this would be a breaking change and should only be implemented in Trubudget 2.0.0.

[Stezido]

TODOs:

• in production remove restore/backup endpoint
• in non prod mode remove deprecated backup endpoint and use v2 as v1 Modify backup endpoint to not accept versions older than TB 2.0 #1076