Supplement attributes before import.
This means prompting the user for things like labels and the like. The needed attributes will have been passed to supplement_prep.
This method prompts the user and fills in the attributes. If the user or cancellable cancels the operation the error should be set with g_io_error_cancelled.
this |
the interaction |
builder |
supplemented attributes |
cancellable |
optional cancellable object |
g_tls_interaction_handled if successful or g_tls_interaction_failed |