Bugfix
If an attribute has a ForeignKeyStorage and there is a "reverse attribute" for this attribute, this reverse attribute cannot be preloaded.
The reason for this is that the ReverseStorage only offers a preload or reverse preload if the forward storage is an AssociationStorage.
Solution
The APIs getPreload and getReversePreload already exist in StorageImplementation. The corresponding other preload of the forward attribute can be used here.