feat: provide an unmanaged switch

Also alias `port` to support both `port` and `ports` as per the nmstate spec.

Reviewed-on: NationTech/harmony#186

harmony/src/infra/brocade.rs

@@ -113,6 +113,37 @@ impl SwitchClient for BrocadeSwitchClient {
     }
 }
 
+#[derive(Debug)]
+pub struct UnmanagedSwitch;
+
+impl UnmanagedSwitch {
+    pub async fn init( ) -> Result<Self, ()> {
+        Ok(Self)
+    }
+}
+
+#[async_trait]
+impl SwitchClient for UnmanagedSwitch {
+    async fn setup(&self) -> Result<(), SwitchError> {
+        todo!("unmanaged switch. Nothing to do.")
+    }
+
+    async fn find_port(
+        &self,
+        mac_address: &MacAddress,
+    ) -> Result<Option<PortLocation>, SwitchError> {
+        todo!("unmanaged switch. Nothing to do.")
+    }
+
+    async fn configure_port_channel(
+        &self,
+        channel_name: &str,
+        switch_ports: Vec<PortLocation>,
+    ) -> Result<u8, SwitchError> {
+        todo!("unmanaged switch. Nothing to do.") 
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::sync::{Arc, Mutex};