Expose/get internal address

[xsats]

Description

Until this PR, bdk-ffi get_address did not support internal/change addresses. Any sufficiently advanced wallet will need this functionality, or be indistinguishable from an insufficiently-advanced wallet.

Notes to the reviewers

I created a separate mapping for get_internal_address instead of adding another field to get_address, which matches the existing bdk naming pattern and keeps the exposed get_{x_}address methods from being cluttered.

Changelog notice

Add wallet::get_internal_addresses API

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

[thunderbiscuit]

Approach ACK. Great addition to the API. It reminded me that I had in mind of taking all methods on the Wallet type one by one and asking myself "is there a reason to keep this out of the bindings?". In this case clearly there are none. Happy to see it added.

Similar to 305, you'll need to remove the to_string() calls in the test to pass the Clippy CI, and I'd like to have the Kotlin API docs fixed before merging. As mentioned in #305, I'm happy to do it, just let me know.

[xsats]

Thanks again, happy to fix this too. Can also help with adding other absent APIs.

From my standpoint this and #305 are definite candidates, and simple to implement so I jumped straight to PRs. But will open issues for any 'contentious' additions in terms of whether they're needed, or if there're multiple clear implementation variants etc.

[xsats]

and I'd like to have the Kotlin API docs fixed before merging. As mentioned in #305, I'm happy to do it, just let me know.

Similarly, if you don't mind adding for now that would be great thanks.

[thunderbiscuit]

One small fix to the tests is required.

[thunderbiscuit]

ACK aa842c3.

[notmandatory]

ACK aa842c3

Concept and code looks good!