mixins library Null safety

Mixins

DeleteAllMixin<T extends OfflineFirstModel>
Adds functions deleteAll and deleteAllExcept
DestructiveLocalSyncFromRemoteMixin<T extends OfflineFirstModel>
Provides an extended get method to support remote syncs that override local data. For example, if two models exist in the remoteProvider but three exist in sqliteProvider and memoryCacheProvider, the extra model is removed from the local providers when #get:forceLocalSyncFromRemote is true or when destructiveLocalSyncFromRemote is invoked. [...]