I have an old application which I want to add the bootloader and secure DFU. I have to migrate to SDK version 12 and I have some persistent data which the old program is writing to locations 0x79000 to 0x7D000. I don't want to do any special memory manipulation while doing the update via BLE and DFU. What should I do with that "user" memory? Is it safe to leave there or should I use the fstorage module since the pstorage module was removed?