Suggestions

1. Validation of full inheritance path in OfType<T> filter, to handle rare cases where documents with different/non existent full paths but same/existent leaf present:
   1. Collections with [A_nonexistent, B_nonexistent, C_existent] documents
      1. Due to corruption/leftovers
      2. Collections shared among mult. apps.
   2. Collections with [X, Y, C] [A, B, C] documents, where [X, Y, C] and [A, B, C] are in different namespaces

1. Forbid upsert of abstract classes and interfaces
2. Consider forbidding instantiating objects with non existent inheritance paths. For example C with _t: [A_nonexistent, B_nonexistent, C_existent] discriminator