* `Additions` now implements `Append` and uses `Append` to implement
`append()`.
* `append()` logic enforces that `last_seen` values should only
increase.
* Test written for `append()` with `last_seen` behaviour.
Instead of forcing all transactions inserted to use the same anchors, we
change the API to have unique anchors per transaction.
This allows for more flexibility in general. For example, use `Anchor`
implementations that contain the position in a block of a transaction.
The `insert_relevant_txs` test has also been changed to used
`KeychainTxOutIndex` so that index additions can be checked
(`SpkTxOutIndex` has no additions).
Additionally, generic bounds of some `IndexedTxGraph` list methods have
been fixed.
This is mostly copying over the relevant tests from `SparseChain`.
Changes are made to `local_chain::ChangeSet` to re-add the ability to
remove blocks.
Previously, I have misunderstood the definition of anchor. If a tx is
anchored in a block, it does not necessarily mean it is confirmed in
that block. The tx can be confirmed in an ancestor block of the anchor
block.
With this new definition, we need a new trait `ConfirmationHeight` that
has one method `confirmation_height`. This trait can be used to extend
`Anchor` for those implementations that can give us the exact
conirmation height of a tx (which is useful in most cases).
Another change is to add another variant to the `ObservedAs` enum;
`ObservedAs::ConfirmedImplicit(A)`. If a tx does not have an anchor, but
another tx that spends it has an anchor that in in the best chain, we
can assume that tx is also in the best chain. The logic of
`TxGraph::try_get_chain_position` is also changed to reflect this.
Some methods from `IndexedTxGraph` have been moved to `TxGraph` as they
do not require the `Indexer`. Some `TxGraph` methods have been renamed
for clarity and consistency.
Also more docs are added.
Methods of old structures that return transaction(s) no longer return
`TxNode`, but `Transaction` as done previously.
`TxInGraph` is renamed to `TxNode`, while the internal `TxNode` is
renamed to `TxNodeInternal`.
* Introduce `GraphedTx` struct to access transaction data of graphed
transactions.
* Ability to insert/access anchors and "seen at" values for graphed
transactions.
* `Additions` now records changes to anchors and last_seen_at.
