Auto merge of #4366 - str4d:z_viewtransaction-release-notes, r=str4d

Add release notes for z_viewtransaction

doc/release-notes.md

@@ -4,6 +4,34 @@ release-notes at release time)
 Notable changes
 ===============
 
+View shielded information in wallet transactions
+------------------------------------------------
+
+In previous `zcashd` versions, to obtain information about shielded transactions
+you would use either the `z_listreceivedbyaddress` RPC method (which returns all
+notes received by an address) or `z_listunspent` (which returns unspent notes,
+optionally filtered by addresses). There were no RPC methods that directly
+returned details about spends, or anything equivalent to the `gettransaction`
+method (which returns transparent information about in-wallet transactions).
+
+This release introduces a new RPC method `z_viewtransaction` to fill that gap.
+Given the ID of a transaction in the wallet, it decrypts the transaction and
+returns detailed shielded information for all decryptable new and spent notes,
+including:
+
+- The address that each note belongs to.
+- Values in both decimal ZEC and zatoshis.
+- The ID of the transaction that each spent note was received in.
+- An `outgoing` flag on each new note, which will be `true` if the output is not
+  for an address in the wallet.
+- A `memoStr` field for each new note, containing its text memo (if its memo
+  field contains a valid UTF-8 string).
+
+Information will be shown for any address that appears in `z_listaddresses`;
+this includes watch-only addresses linked to viewing keys imported with
+`z_importviewingkey`, as well as addresses with spending keys (both generated
+with `z_getnewaddress` and imported with `z_importkey`).
+
 Build system
 ------------