[fix] Django files, null value
Bug prevention
File validations, meta

* File field now expects file meta to be sent
File, meta, facultative

* File meta is expected but not required
Non-sctrict schema checks

* Only attributes that were sent are saved on edit
[fix] Create decorator
[fix] Default values as methods

* If a callable object is passed as default value, it is called
Drop debug messages
Dropping objects
Collections, not strict

* No changes are made to collections in non strict mode if not sent