[0.4.0] - 2022-11-12
--------------------

Added
- Implementations of `zcash_client_backend::data_api::WalletReadTransparent`
  and `WalletWriteTransparent` have been added. These implementations
  are available only when the `transparent-inputs` feature flag is
  enabled.
- New error variants:
  - `SqliteClientError::TransparentAddress`, to support handling of errors in
    transparent address decoding.
  - `SqliteClientError::RequestedRewindInvalid`, to report when requested
    rewinds exceed supported bounds.
  - `SqliteClientError::DiversifierIndexOutOfRange`, to report when the space
    of available diversifier indices has been exhausted.
  - `SqliteClientError::AccountIdDiscontinuity`, to report when a user attempts
    to initialize the accounts table with a noncontiguous set of account identifiers.
  - `SqliteClientError::AccountIdOutOfRange`, to report when the maximum account
    identifier has been reached.
  - `SqliteClientError::Protobuf`, to support handling of errors in serialized
    protobuf data decoding.
- An `unstable` feature flag; this is added to parts of the API that may change
  in any release. It enables `zcash_client_backend`'s `unstable` feature flag.
- New summary views that may be directly accessed in the sqlite database.
  The structure of these views should be considered unstable; they may
  be replaced by accessors provided by the data access API at some point
  in the future:
  - `v_transactions`
  - `v_tx_received`
  - `v_tx_sent`
- `zcash_client_sqlite::wallet::init::WalletMigrationError`
- A filesystem-backed `BlockSource` implementation
  `zcash_client_sqlite::FsBlockDb`. This block source expects blocks to be
  stored on disk in individual files named following the pattern
  `<blockmeta_root>/blocks/<blockheight>-<blockhash>-compactblock`. A SQLite
  database stored at `<blockmeta_root>/blockmeta.sqlite`stores metadata for
  this block source.
  - `zcash_client_sqlite::chain::init::init_blockmeta_db` creates the required
    metadata cache database.
- Implementations of `PartialEq`, `Eq`, `PartialOrd`, and `Ord` for `NoteId`

Changed
- Various **BREAKING CHANGES** have been made to the database tables. These will
  require migrations, which may need to be performed in multiple steps. Migrations
  will now be automatically performed for any user using
  `zcash_client_sqlite::wallet::init_wallet_db` and it is recommended to use this
  method to maintain the state of the database going forward.
  - The `extfvk` column in the `accounts` table has been replaced by a `ufvk`
    column. Values for this column should be derived from the wallet's seed and
    the account number; the Sapling component of the resulting Unified Full
    Viewing Key should match the old value in the `extfvk` column.
  - The `address` and `transparent_address` columns of the `accounts` table have
    been removed.
    - A new `addresses` table stores Unified Addresses, keyed on their `account`
      and `diversifier_index`, to enable storing diversifed Unified Addresses.
    - Transparent addresses for an account should be obtained by extracting the
      transparent receiver of a Unified Address for the account.
  - A new non-null column, `output_pool` has been added to the `sent_notes`
    table to enable distinguishing between Sapling and transparent outputs
    (and in the future, outputs to other pools). Values for this column should
    be assigned by inference from the address type in the stored data.
- MSRV is now 1.56.1.
- Bumped dependencies to `ff 0.12`, `group 0.12`, `jubjub 0.9`,
  `zcash_primitives 0.9`, `zcash_client_backend 0.6`.
- Renamed the following to use lower-case abbreviations (matching Rust
  naming conventions):
  - `zcash_client_sqlite::BlockDB` to `BlockDb`
  - `zcash_client_sqlite::WalletDB` to `WalletDb`
  - `zcash_client_sqlite::error::SqliteClientError::IncorrectHRPExtFVK` to
    `IncorrectHrpExtFvk`.
- The SQLite implementations of `zcash_client_backend::data_api::WalletRead`
  and `WalletWrite` have been updated to reflect the changes to those
  traits.
- `zcash_client_sqlite::wallet`:
  - `get_spendable_notes` has been renamed to `get_spendable_sapling_notes`.
  - `select_spendable_notes` has been renamed to `select_spendable_sapling_notes`.
  - `get_spendable_sapling_notes` and `select_spendable_sapling_notes` have also
    been changed to take a parameter that permits the caller to specify a set of
    notes to exclude from consideration.
  - `init_wallet_db` has been modified to take the wallet seed as an argument so
    that it can correctly perform migrations that require re-deriving key
    material. In particular for this upgrade, the seed is used to derive UFVKs
    to replace the currently stored Sapling ExtFVKs (without losing information)
    as part of the migration process.

Removed
- The following functions have been removed from the public interface of
  `zcash_client_sqlite::wallet`. Prefer methods defined on
  `zcash_client_backend::data_api::{WalletRead, WalletWrite}` instead.
  - `get_extended_full_viewing_keys` (use `WalletRead::get_unified_full_viewing_keys` instead).
  - `insert_sent_note` (use `WalletWrite::store_sent_tx` instead).
  - `insert_sent_utxo` (use `WalletWrite::store_sent_tx` instead).
  - `put_sent_note` (use `WalletWrite::store_decrypted_tx` instead).
  - `put_sent_utxo` (use `WalletWrite::store_decrypted_tx` instead).
  - `delete_utxos_above` (use `WalletWrite::rewind_to_height` instead).
- `zcash_client_sqlite::with_blocks` (use
  `zcash_client_backend::data_api::BlockSource::with_blocks` instead).
- `zcash_client_sqlite::error::SqliteClientError` variants:
  - `SqliteClientError::IncorrectHrpExtFvk`
  - `SqliteClientError::Base58`
  - `SqliteClientError::BackendError`

Fixed
- The `zcash_client_backend::data_api::WalletRead::get_address` implementation
  for `zcash_client_sqlite::WalletDb` now correctly returns `Ok(None)` if the
  account identifier does not correspond to a known account.

Deprecated
- A number of public API methods that are used internally to support the
  `zcash_client_backend::data_api::{WalletRead, WalletWrite}` interfaces have
  been deprecated, and will be removed from the public API in a future release.
  Users should depend upon the versions of these methods exposed via the
  `zcash_client_backend::data_api` traits mentioned above instead.
  - Deprecated in `zcash_client_sqlite::wallet`:
    - `get_address`
    - `is_valid_account_extfvk`
    - `get_balance`
    - `get_balance_at`
    - `get_sent_memo`
    - `block_height_extrema`
    - `get_tx_height`
    - `get_block_hash`
    - `get_rewind_height`
    - `get_commitment_tree`
    - `get_witnesses`
    - `get_nullifiers`
    - `insert_block`
    - `put_tx_meta`
    - `put_tx_data`
    - `mark_sapling_note_spent`
    - `put_receiverd_note`
    - `insert_witness`
    - `prune_witnesses`
    - `update_expired_notes`
    - `get_address`
  - Deprecated in `zcash_client_sqlite::wallet::transact`:
    - `get_spendable_sapling_notes`
    - `select_spendable_sapling_notes`