I have 2 entities User and Location with a Many-to-Many link. The creation of a relationship seems to work but not the deletion.
The goal is not to delete the entities but only the relationships.

Should the deletion be done on both entities?
Only the one with the @Backlink?

I have tried several solutions based on .remove() + put() but without success.

@Entity()
class LocationModel {
  @Id()
  int localId = 0;

  @Unique(onConflict: ConflictStrategy.replace)
  int id;

  @Backlink('location')
  final items = ToMany<ItemModel>();

  final users = ToMany<UserModel>();
}


@Entity()
class UserModel {
  @Id()
  int localId = 0;

  @Unique(onConflict: ConflictStrategy.replace)
  String guid;

  @Backlink('user')
  final items = ToMany<ItemModel>();

  @Backlink()
  final locations = ToMany<LocationModel>();
}

A method comes to update the relationships between the location and the users. Users is the list of users of the location (given by an API). The goal is to update the relationships (and only the relationships).

The idea will also be to do something similar with a method in the user collection to have a User and a list of Location to come update.

 LocationModel updateUsers(
   LocationModel locationModel, 
   List<UserModel> users,
 ) {
    // Update users that may still have a link to this location
    final usersByLocation = userCollection.getByLocation(locationModel.localId);

    // Remove relationship with location if no users (users.isEmpty) or no longer present in users list
    final userToRemoveLocation = users.isEmpty
        ? usersByLocation
        : usersByLocation
            .where((user) => !users.any((u) => u.guid == user.guid))
            .toList();

    for (var user in userToRemoveLocation) {
      user.locations.remove(locationModel);
      userCollection.put(user);

      final locationInDb = locationBox.get(locationModel.localId);
      if (locationInDb != null) {
        locationInDb.users.remove(user);
        locationBox.put(locationInDb);
      }
    }

    // Creation of new relationships between location and users (users list)
    for (var user in users) {
      final userInDb = userCollection.getByServerId(user.guid);
      if (userInDb != null) {
        userInDb.locations.add(locationModel);
        userCollection.put(userInDb);

        final locationInDb = locationBox.get(locationModel.localId);
        if (locationInDb != null) {
          locationInDb.users.add(user);
          locationBox.put(locationInDb);
        }
      }
    }

    return locationModel;
  }