Add BDK-based KeysManager example

[tnull]

This introduces a basic Rust example on how to wrap KeysManager in order to make outputs spendable by a BDK wallet.

Probably not complete as it needs to be complemented with Java/Kotlin counterparts.

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[tnull]

Will also need a rebase after lightningdevkit/rust-lightning#1910 / lightningdevkit/rust-lightning#1930 got in.

[ConorOkus]

@tnull I think this might be good to go. We don't need to wait for Java/Kotlin examples but I'm currently implementing in kotlin now so should have it shortly. I just created a discussion to make sure I'm implementing it right.

[tnull]

@tnull I think this might be good to go. We don't need to wait for Java/Kotlin examples but I'm currently implementing in kotlin now so should have it shortly. I just created a discussion to make sure I'm implementing it right.

Heh, have to admit I've almost forgotten about this one. Updated for the recent removal of KeysInterface.

@wpaulino Any thoughts what else to add while I'm here? Possibly more specifics regarding the individual SignerProvider/NodeSigner/EntropySource trinity?

[wpaulino]

@wpaulino Any thoughts what else to add while I'm here? Possibly more specifics regarding the individual SignerProvider/NodeSigner/EntropySource trinity?

Not really, I think the example you've added is good enough. Realistically, users won't be implementing their own versions of these traits other than the common case already covered here, and on the rare case they need to, the rust docs should help.

[tnull]

Not really, I think the example you've added is good enough. Realistically, users won't be implementing their own versions of these traits other than the common case already covered here, and on the rare case they need to, the rust docs should help.

Yeah, was thinking whether generally something came to mind we want to add here regarding keys management etc., but probably it's fine to land this as-is for now.

[tnull]

@ConorOkus Did you end up making any progress on the Java side of things?

[ConorOkus]

@ConorOkus Did you end up making any progress on the Java side of things?

No but let's merge this, I've created and issue to follow up with those examples. cc @Roy0Anonymous to add Swift example

[tnull]

No but let's merge this, I've created and issue to follow up with those examples. cc @Roy0Anonymous to add Swift example

Alright, updated as there were minor interface changes since this PR was opened.