rpc: Add JSON-RPC methods for working with PCZTs

CHANGELOG.md

@@ -30,6 +30,18 @@ be considered breaking changes.
   of a v6 transaction under a new `ironwood` key. Ironwood actions are
   Orchard-shaped, so the object has the same shape as the existing `orchard` one.
   Previously the Ironwood bundle was omitted from the decoded output.
+- JSON-RPC methods for working with PCZTs (Partially Created Zcash
+  Transactions), the robust replacements for `createrawtransaction`,
+  `fundrawtransaction`, and `signrawtransaction`. A transaction is assembled by
+  threading a PCZT through these roles:
+  - `pczt_create` — build a PCZT from a payment request (select inputs and
+    compute change), the replacement for `createrawtransaction` +
+    `fundrawtransaction`.
+  - `pczt_combine` — merge the contributions of several parties into one PCZT.
+  - `pczt_prove` — add the Sapling and/or Orchard zero-knowledge proofs.
+  - `pczt_sign` — add signatures using the wallet's keys.
+  - `pczt_extract` — verify the PCZT and extract the final, network-ready
+    transaction.
 
 ### Changed
 

Cargo.toml

@@ -115,6 +115,15 @@ zcash_protocol = "0.10.0-pre.0"
 
 # Zcash payment protocols
 orchard = "0.15.0-pre.2"
+pczt = { version = "0.7", features = [
+    "orchard",
+    "sapling",
+    "transparent",
+    "prover",
+    "signer",
+    "spend-finalizer",
+    "tx-extractor",
+] }
 sapling = { package = "sapling-crypto", version = "0.7" }
 transparent = { package = "zcash_transparent", version = "0.9.0-pre.0" }
 zcash_encoding = "0.4"
@@ -177,6 +186,7 @@ zcash_encoding = { git = "https://github.com/zcash/librustzcash.git", rev = "29c
 # NOTE: zcash_history is deliberately NOT patched here: the root graph does not
 # use it (only the backend workspaces do, and their patch blocks carry it).
 zcash_keys = { git = "https://github.com/zcash/librustzcash.git", rev = "29c7fb28889a69df15b44fc9465cf4a464f766e9" }
+pczt = { git = "https://github.com/zcash/librustzcash.git", rev = "29c7fb28889a69df15b44fc9465cf4a464f766e9" }
 zcash_primitives = { git = "https://github.com/zcash/librustzcash.git", rev = "29c7fb28889a69df15b44fc9465cf4a464f766e9" }
 zcash_proofs = { git = "https://github.com/zcash/librustzcash.git", rev = "29c7fb28889a69df15b44fc9465cf4a464f766e9" }
 zcash_protocol = { git = "https://github.com/zcash/librustzcash.git", rev = "29c7fb28889a69df15b44fc9465cf4a464f766e9" }