Support taproot PSBTs

    Sometimes taproot signers leave around taproot signing artifacts.
    Part of the spec is to remove unnecessary psbt data for counterparties,
    so this ensures removal of taproot variety unnecessary data too.

payjoin/src/receive/mod.rs

@@ -800,6 +800,7 @@ impl ProvisionalProposal {
             self.payjoin_psbt.inputs[i].witness_utxo = None;
             self.payjoin_psbt.inputs[i].final_script_sig = None;
             self.payjoin_psbt.inputs[i].final_script_witness = None;
+            self.payjoin_psbt.inputs[i].tap_key_sig = None;
         }
         Ok(PayjoinProposal {
             payjoin_psbt: self.payjoin_psbt,

payjoin/src/send/mod.rs

@@ -988,11 +988,18 @@ fn clear_unneeded_fields(psbt: &mut Psbt) {
     psbt.unknown_mut().clear();
     for input in psbt.inputs_mut() {
         input.bip32_derivation.clear();
+        input.tap_internal_key.clear();
+        input.tap_key_origins.clear();
+        input.tap_key_sig.clear();
+        input.tap_merkle_root.clear();
+        input.tap_script_sigs.clear();
         input.proprietary.clear();
         input.unknown.clear();
     }
     for output in psbt.outputs_mut() {
         output.bip32_derivation.clear();
+        output.tap_internal_key.clear();
+        output.tap_key_origins.clear();
         output.proprietary.clear();
         output.unknown.clear();
     }