How to write to GATT with protocomm_nimble when using the wifi provisioning example

[karunt]

I want a mobile app to detect changes in the wifi provisioning life cycle and any errors the wifi provisioning process runs into to inform an end user of what's happening with the wifi provisioning process. For that to happen, I'm assuming the app will somehow need to read values written to a GATT endpoint? I can't figure out how the wifi provisioning example, which seems to use the protocomm_nimble protocol, writes to a GATT endpoint. What are the relevant functions that achieve this? Or would I have to combine code from the GATT server example (under bluetooth/bluedroid/ble/gatt_server_service_table) with the wifi provisioning example to be able to write to GATT?