fun KeyPair.signWithECDSA(bytesToSign: ByteArray): WithKey
fun KeyPair.signWithECDSA(bytesToSign: OpaqueBytes): WithKey
fun KeyPair.signWithECDSA(bytesToSign: OpaqueBytes, party: Party): LegallyIdentifiable
fun KeyPair.signWithECDSA(bytesToSign: ByteArray, party: Party): LegallyIdentifiable