* Add prototype contract implementation
Lacks:
- Payment proofs (add early payment proofs)
- Tests
- Better structure
* Separate contract utilities
* Simplify the main setup/sign code flow
* Remove commented initial_sec_key assignment
* Simplify sign::compute function
* Add logic for "removal" of secret keys from the context
* Further simplify a bit sign and setup
* No need for mutable context when adding outputs
* Refactor the commented code (lol)
* Refactor a bit
* tmp
---------
Co-authored-by: oryhp <gtrphyro@gmail.com>
