Jack Grigg

Per the meeting today, this PR needs to be rebased on `main` and squashed down. Then once we're happy with it as a framework, we can merge it, and then...

Assigned ZIP 270 in ZIP Sync today by a quorum of ZIP Editors (@nuttycom, @arya2 and myself).

Cross-referencing: #1034 and #1036 were in service of enabling ZSAs to benefit from this ZIP.

I see in the `wealthfolio-v2` branch there is a new [`wealthfolio_core::activities::activities_constants`](https://github.com/afadil/wealthfolio/blob/wealthfolio-v2/src-core/src/activities/activities_constants.rs) module. This would be an ideal place to document the activity types for v2.

See also our comment on the almost idential ZIP https://github.com/zcash/zips/pull/866#discussion_r1663195185.

As a helpful visualization, this is what the flow of ZEC within a coinbase transaction for a single block looks like (as percentages overall; the halving effect is not shown...

AFAICT the linked PR has still not been released; this is blocked on https://github.com/zcash/lightwalletd/issues/517 (and subsequent deployment).

> > * `batch.rs` has 1 non-test unwrap This (along with one unwrap in `prunable.rs`) is due to `BatchInsertionResult.max_insert_position` being an `Option`, but I cannot find anywhere this gets set...

> This should be justifiable because of the invariant that you cannot construct a witness for an empty tree. However, `incrementalmerkletree::witness::IncrementalWitness` does permit construction from an empty tree, so we...

> This fix was copied from: https://github.com/nerdcash/Nerdbank.Cryptocurrencies/pull/262/files#diff-7cc5f1ef7cbfce3114fe631861f19de2c050c13ff71e987100669131bb9ffa25 That fix is itself copied from my fix here: https://github.com/Electric-Coin-Company/zcash-android-wallet-sdk/commit/1bf2f848373bee833a11fbb8cd9b570218ac71bb (and the majority of the text in this PR's OP and commit message...