message: [config] use derived default when possible
  SecureConfig can derive default at no loss
  Closes:
  Approved by: joshlind
diff: @@ -7,20 +7,12 @@ use std::{net::SocketAddr, path::PathBuf};
  const DEFAULT_JSON_RPC_ADDR: &str = "127.0.0.1";
  const DEFAULT_JSON_RPC_PORT: u16 = 8080;
  -#[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
  +#[derive(Clone, Debug, Default, Deserialize, PartialEq, Serialize)]
  #[serde(default, deny_unknown_fields)]
  pub struct SecureConfig {
  pub key_manager: KeyManagerConfig,
  }
  -impl Default for SecureConfig {
  - fn default() -> Self {
  - Self {
  - key_manager: KeyManagerConfig::default(),
  - }
  - }
  -}
  -
  #[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
  #[serde(default, deny_unknown_fields)]
  pub struct KeyManagerConfig {
  