Function default_config 

pub fn default_config(
    environment: &Environment,
    rpc_url: Option<String>,
    region: Option<Region>,
) -> Result<Config, WalletKitError>

Builds a Config for the given Environment using direct (non-OHTTP) service endpoints — the default for SDK consumers.

Errors

Returns WalletKitError if the configuration cannot be constructed (e.g. invalid RPC URL).