Write an example in the examples directory with the workflow from BIP174. See the valid example that starts from the line in the above link.

The private keys in the tests below are derived from the following master private key:

• Use BIP32 wallet APIs to derive all priv/public keys
• Use the sighash APIs to compute the signature hashes
• Use all Psbt supported APIs
• Identify the API pain-points and suggest improvements.