Fix sFTP for Postgres

[talavis]

Describe the pull request:

• Bug fix
• Functional change
• New feature
• Code cleanup
• Build system change
• Documentation change
• Language translation

Pull request long description:

Updated the generate sFTP credentials functions to use digest() instead of SHA2, including a workaround to remove the prefix '\x' from the generated hash.

Also removes the non-functional sFTP tab from the dataset admin page.

[norling]

You can cast the hash to a hex value (removing the prefix) with passwd_hash = fn.encode(fn.digest(password, 'sha256'), 'hex'). Looks good otherwise!