Build customized FOTA Service

We want to build the FOTA service like AirVantage. The service only need to update and upgrade the system or apps. Is it able to use the current legato API like le_fwupdate_interface for building the customized service?

how about directly sending AT command AT+WDSS=1 to connect to the Airvantage server?

Another method is to use the AirVantage Connector API: