Add transformation helpers to reference implementation

[pablo-de-andres]

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[pablo-de-andres]

I replaced SimPARTIX by the sleep command and a dummy template file (not really used, just created for demonstration) to simulate an actual transformation. Let me know if you had something else in mind for the reference @csadorf.

[csadorf]

@pablo-de-andres I've refactored the code and implemented the routes and tests. Those are the remaining tasks:

• Rebase on main (unless we merge Reference-implementations/object-storage #19 first)
• Better modularize the tests.