add? should depend on the *embedded* model's state, not the containing model's.
(which don't come from the database)
…on't have to define a new one
At the same time, simplified EmbeddedModelField.pre_save and .get_db_prep_save.
…tributed by Jonas Haag.
…save (and also happens *before* any data type conversions). Also fixes the code accordingly. Contributed by Jonas Haag.
…tion method, plus one fix to make the tests pass (nice error messages should also be used in the "untyped" case) Contributed by Jonas Haag.