@Override
    public void setProvisioningAuthentication(@NonNull final String authentication) {
        mMeshProvisioningHandler.sendProvisioningConfirmation(authentication);
    }
Appends the PDUs that are segmented at gatt layer.

@param mtuSize mtu size supported by the device/node
@param pdu     pdu received by the provisioner
@return the combine pdu or returns null if not complete.
mesh/src/main/java/no/nordicsemi/android/mesh/MeshManagerApi.java