Function unwrap_signing_key_pkcs8 

pub async fn unwrap_signing_key_pkcs8(
    variant: EcdsaVariant,
    input: UnwrapInput,
    options: SigningKeyOptions,
) -> Result<SigningKey, Error>

Mint a signing key from unwrapped key material read as a PKCS#8 PrivateKeyInfo, subject to import_signing_key_pkcs8’s contract. Consumes the UnwrapInput; the minted key’s usages and extractability come from options alone.