Function import_signing_key_pkcs8 

pub async fn import_signing_key_pkcs8(
    variant: EcdsaVariant,
    pkcs8: impl Into<Vec<u8>>,
    options: SigningKeyOptions,
) -> Result<SigningKey, Error>

Import a signing key as a PKCS#8 PrivateKeyInfo (DER, the SEC1 private-key body). The encoded curve must match the declared variant’s (Error::InvalidKey); an embedded public key, when present, is validated against the scalar and never trusted on its own. Returns only the signing key; the public half is imported separately (there is no derive from a private import — see the WIT ecdsa-sign interface doc).