Let serde use defaults for LoraCloudModemGeolocationServices.

This lets serde use default values in case a field is missing.
Specifically, this fixes the 'missing field `forward_f_ports`'
if migrating from an older LoRa Cloud configuration where the
`forward_f_ports` field was not yet present.

chirpstack/src/storage/application.rs

@@ -201,6 +201,7 @@ pub struct LoraCloudConfiguration {
 }
 
 #[derive(Default, Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(default)]
 pub struct LoraCloudModemGeolocationServices {
     pub token: String,
     pub modem_enabled: bool,