clean code with clippy

src/model/logbook.rs

@@ -118,7 +118,7 @@ pub enum LogbookCreateError {
     BoatLocked,
     BoatNotFound,
     TooManyRowers(usize, usize),
-    RowerAlreadyOnWater(User),
+    RowerAlreadyOnWater(Box<User>),
     RowerCreateError(i64, String),
     ArrivalNotAfterDeparture,
     SteeringPersonNotInRowers,
@@ -386,7 +386,7 @@ ORDER BY departure DESC
             let user = User::find_by_id(db, *rower as i32).await.unwrap();
 
             if user.on_water(db).await {
-                return Err(LogbookCreateError::RowerAlreadyOnWater(user));
+                return Err(LogbookCreateError::RowerAlreadyOnWater(Box::new(user)));
             }
         }