Remove unneeded clones

src/device_id.rs

@@ -10,7 +10,7 @@ pub type DeviceId = String;
 
 /// Generates a random `DeviceId`, suitable for assignment to a new device.
 pub fn generate() -> DeviceId {
-    generate_localpart(8).to_string()
+    generate_localpart(8)
 }
 
 #[cfg(test)]

src/user_id.rs

@@ -131,7 +131,7 @@ impl<'a> TryFrom<&'a str> for UserId {
         Ok(Self {
             hostname: host,
             port,
-            localpart: downcased_localpart.to_owned(),
+            localpart: downcased_localpart,
         })
     }
 }