* Implement sighash
* move sighash logic to a separate module
* start filling in more of the alg
* start setting up a test case
* make the test useful
* Iter transaction inputs
* better error message for expect
* add support for zip243 sighash
* ohey first testvector is passing, yayyy
* pass the second testvector
* add last testvector
* move a use statement
* use common deserialization code for amount everywhere
* cleanup attributes
* bring in fixed preimage
* fix discrepancy with spec
* always deserialize as a signed value
* Update zebra-chain/src/transaction/sighash.rs
* update unreachable statements
* add serialization impls for nonnegative amounts
* Apply suggestions from code review
* document sighash fn
* tweek docs
* fix mistake in translation for zip243
* consistent error messages
* reorder because i like it more that way
* document more panics
* Update zebra-chain/src/amount.rs
* Add comment regarding the serialization of spend descriptions in sighash
Co-authored-by: teor <teor@riseup.net>
Co-authored-by: Deirdre Connolly <deirdre@zfnd.org>
Jane Lusby
Henry de Valence