Change default tx to version 2

[benalleng]

Description

Changes the default version number to version 2 to enchance privacy for the type of wallet used

Fixes #1676

Changelog notice

• Changed the default transaction version number in the transaction builder.
• Updated the test to test for the default transaction number.

Checklists

All Submissions:

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

[benalleng]

Should any of the tests be updated to use a version 2 tx after setting it as a new default?

[ValuedMammal]

Should any of the tests be updated to use a version 2 tx after setting it as a new default?

You could possibly add an assertion to one of the existing tests in tests/wallet.rs to check that transactions we create are using the new default.

[ValuedMammal]

Thanks @benalleng overall this looks good to me. My only comment is I think some additional cleanups can be done like using bitcoin::transaction::Version everywhere internally instead of this roundabout way that we're doing now. But I'm ok with pushing that to a followup since this PR effectively resolves the current issue.

bdk/crates/wallet/src/wallet/mod.rs

Lines 1390 to 1395 in 4a3675f

	let mut tx = Transaction {
	version: transaction::Version::non_standard(version),
	lock_time,
	input: vec![],
	output: vec![],
	};

[benalleng]

Just to confirm you had meant removing the version default in the tx_builder completely in favor of the bitcoin::transaction::Version?

[notmandatory]

Overall this looks good, but should be squashed into one or at most two commits with "conventional commit" style messages. Something like:

fix(tx_builder): change default transaction version to 2

This change improves privacy since >85% of transactions on the network are version 2. Version 2 is also necessary to eventually implement BIP 326 nSequence-based anti-fee-sniping.

[notmandatory]

ACK 2219b7c

[benalleng]

Thanks for holding my hand through this one!