zcash_client_backend: Make AccountId an associated type of `WalletR…

…ead`

This PR was extracted from zcash#1175
in order to make the changes to `zcash_client_backend` usable without
the additional generalizations to `zcash_client_sqlite` made by that PR.

Co-authored-by: Andrew Arnott <[email protected]>

zcash_client_backend/CHANGELOG.md

@@ -56,6 +56,7 @@ and this library adheres to Rust's notion of
     }`
   - `WalletSummary::next_sapling_subtree_index`
   - `wallet`:
+    - `Account`
     - `propose_standard_transfer_to_address`
     - `create_proposed_transactions`
     - `input_selection`:
@@ -96,6 +97,41 @@ and this library adheres to Rust's notion of
   - `parse::Param::name`
 
 ### Changed
+- Several structs and functions now take an `AccountId` type parameter
+  parameter in order to decouple the concept of an account identifier from
+  the ZIP 32 account index. Many APIs that previously referenced
+  `zcash_primitives::zip32::AccountId` now reference the generic type.
+  Impacted types and functions are:
+  - `zcash_client_backend::data_api`:
+    - `WalletRead::{
+        get_account_birthday,
+        get_current_address,
+        get_unified_full_viewing_keys,
+        get_account_for_ufvk,
+        get_wallet_summary,
+        get_sapling_nullifiers,
+        get_transparent_receivers,
+        get_transparent_balances,
+        get_account_ids
+      }`
+    - `ScannedBlock`
+    - `DecryptedTransaction`
+    - `SentTransaction`
+    - `SentTransactionOutput`
+    - `WalletWrite::create_account`
+    - `WalletWrite::get_next_available_address`
+    - `wallet::InputSelector::propose_transaction`
+    - `wallet::propose_transfer`
+    - `wallet::propose_standard_transfer_to_address`
+  - `zcash_client_backend::decrypt`
+    - `DecryptedOutput`
+    - `decrypt_transaction`
+  - `zcash_client_backend::scanning::scan_block`
+  - `zcash_client_backend::wallet`:
+    - `Recipient`
+    - `WalletTx`
+    - `WalletSaplingSpend`
+    - `WalletSaplingOutput`
 - `zcash_client_backend::data_api`:
   - `BlockMetadata::sapling_tree_size` now returns an `Option<u32>` instead of
     a `u32` for future consistency with Orchard.
@@ -114,6 +150,8 @@ and this library adheres to Rust's notion of
   - `WalletSummary::new` now takes an additional `next_sapling_subtree_index`
     argument.
   - Changes to the `WalletRead` trait:
+    - Added associated type `AccountId`.
+    - Added `get_account` function.
     - `get_checkpoint_depth` has been removed without replacement. This is no
       longer needed given the change to use the stored anchor height for
       transaction proposal execution.
@@ -273,7 +311,7 @@ and this library adheres to Rust's notion of
 ### Removed
 - `zcash_client_backend::wallet`:
   - `ReceivedSaplingNote` (use `zcash_client_backend::ReceivedNote` instead).
-  - `input_selection::{Proposal, ProposalError}` (moved to
+  - `input_selection::{Proposal, ShieldedInputs, ProposalError}` (moved to
     `zcash_client_backend::proposal`).
   - `SentTransactionOutput::sapling_change_to` - the note created by an internal
     transfer is now conveyed in the `recipient` field.