chore: refactor new role rankings code

crates/core/database/src/models/servers/model.rs

@@ -253,6 +253,33 @@ impl Server {
             Err(create_error!(NotFound))
         }
     }
+
+    /// reorders the server's roles rankings
+    pub async fn update_role_rankings(&mut self, db: &Database, new_order: Vec<String>) -> Result<()> {
+        // new_order must always contain every role
+        debug_assert_eq!(self.roles.len(), new_order.len());
+
+        // set the role's ranks to the positions in the vec
+        for (rank, id) in new_order.iter().enumerate() {
+            self.roles.get_mut(id).unwrap().rank = rank as i64;
+        }
+
+        db.update_server(
+            &self.id,
+            &PartialServer {
+                roles: Some(self.roles.clone()),
+                ..Default::default()
+            },
+            Vec::new()
+        ).await?;
+
+        // publish bulk update event
+        EventV1::ServerRoleRanksUpdate {
+            ranks: new_order
+        }.p(self.id.clone()).await;
+
+        Ok(())
+    }
 }
 
 impl Role {