Make Command system more flexible

src/bot/command/hidden.rs

@@ -0,0 +1,23 @@
+use async_trait::async_trait;
+
+use crate::api::Message;
+
+use super::{Command, Context};
+
+pub struct Hidden<C>(pub C);
+
+#[async_trait]
+impl<B, E, C> Command<B, E> for Hidden<C>
+where
+    B: Send,
+    C: Command<B, E> + Send + Sync,
+{
+    fn description(&self, _ctx: &Context) -> Option<String> {
+        // Default implementation, repeated here for emphasis.
+        None
+    }
+
+    async fn execute(&self, arg: &str, msg: &Message, ctx: &Context, bot: &mut B) -> Result<(), E> {
+        self.0.execute(arg, msg, ctx, bot).await
+    }
+}