Clippy was unhappy:
```text
error: use of `.unwrap_or_else(..)` to construct default value
--> sdk/src/signer/keypair.rs:171:27
|
171 | let derivation_path = derivation_path.unwrap_or_else(DerivationPath::default);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `derivation_path.unwrap_or_default()`
|
= note: `-D clippy::unwrap-or-else-default` implied by `-D warnings`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_or_else_default
```
* Fix spelling
* Add validator for SignerSources
* Add helper to generate Keypair from supporting SignerSources
* Add bip32 support to solana-keygen recover
* Make SignerSourceKind const strs, use for Debug impl and URI schemes
