Introduce broadcast queue.

[evanlinjin]

Fixes #40

Description

This PR builts on top of #208 and bitcoindevkit/bdk#1808.

The goal is to evaluate whether the changes introduced in bitcoindevkit/bdk#1808 provide a sufficient foundation to implement and maintain a broadcast queue within bdk_wallet.

Requirements:

• Creating a new tx should not replace unbroadcasted txs that were already in the wallet.

• The broadcast queue should support transaction replacements, with the most recently inserted version taking precedence.

Notes to the reviewers

Design Rationale

For getter-methods on Wallet that requires canonicalization internally, I've opted to pass in CanonicalizationParams as an input. The reasoning is it's up to the application to decide whether or not to include unbroadcasted txs in their UTXO-set/tx-list. There is a method Wallet::include_unbroadcasted() which returns a CanonicalizationParams which would assume all unbroadcasted as canonical.

The alternative would be to pass in a boolean include_unbroadcasted but I felt like it would be more brittle.

Where to start reviewing

The unbroadcasted queue in introduced in a new file wallet/unbroadcasted.rs. Other than that, the majority of the changes are in wallet/mod.rs.

Changelog notice

WIP

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[coveralls]

Pull Request Test Coverage Report for Build 14664394129

Details

• 156 of 238 (65.55%) changed or added relevant lines in 6 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.7%) to 85.823%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
wallet/src/wallet/unbroadcasted.rs	30	64	46.88%
wallet/src/wallet/mod.rs	64	112	57.14%

Files with Coverage Reduction	New Missed Lines	%
wallet/src/wallet/mod.rs	4	82.05%

Totals
Change from base Build 14270666930:	-0.7%
Covered Lines:	7355
Relevant Lines:	8570

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💛 - Coveralls

[evanlinjin]

To Do (as discussed)

• Unexpose CanonicalizationParams from the public API.
• By default, include the whole broadcast queue in assume_canonical.

In the future, if users are requesting that we expose CanonicalizationParam, we can do so via new methods. I.e. transactions_with_params.