Add a "check-config" command to validate config files & tests for it

src/cli/check_config.rs

@@ -0,0 +1,11 @@
+use tracing::info;
+
+use crate::{cli::ConfigArg, config, error};
+
+pub(crate) async fn run(
+    args: ConfigArg,
+) -> Result<(), error::CheckConfigCommand> {
+    let _config = config::load(args.config.as_ref()).await?;
+    info!("Configuration looks good");
+    Ok(())
+}