Let's split the importer in two specialization:
- "representatives": takes a URL or JSON file with representative in the representative formats and create/update them in the contacts database
- "updater": takes a URL or a file in a CSV format and updated the data from it, do not create Contacts.
The updater will not modify the structure of the contact (do not touch the Groups for instance), it will mostly be used to update twitter or phone number of a Contact.
To upload designs, you'll need to enable LFS. More information