More Access to a JsonExportable's Metadata

[adamcesco]

• A motivation for this change

  • Fixes the lack of access to post data that is only accessable through the instagram-private-api (e.g. saved_collection_ids).
  • added get_json_structure(structure: JsonExportable) function to be an attribute of an Instaloader instance. This allows for the access of post data that is not directly accessible through the Instaloader API (e.g. saved_collection_ids).

• The completeness of this change

  • Is it just a proof of concept? No
  • Is the documentation updated (if appropriate)? No
  • Do you consider it ready to be merged or is it a draft? Read to be merged
  • Can we help you at some point? Sure!

[aandergr]

The implementation does not seem well though-through. The Post._iphone_struct method is simply duplicated and private methods are called from outside of the class.