Set "Direct only" to false as default

For android, it is set to true, as multihop is not supported.

Note that in the daemon, the setting is called
`use_multihop_if_necessary` and has the inverse meaning.

android/lib/daemon-grpc/src/main/kotlin/net/mullvad/mullvadvpn/lib/daemon/grpc/ManagementService.kt

@@ -510,10 +510,14 @@ class ManagementService(
 
     suspend fun setDaitaEnabled(enabled: Boolean): Either<SetDaitaSettingsError, Unit> =
         Either.catch {
-                val daitaSettings =
-                    ManagementInterface.DaitaSettings.newBuilder().setEnabled(enabled).build()
-                grpc.setDaitaSettings(daitaSettings)
-            }
+            val daitaSettings =
+                ManagementInterface.DaitaSettings.newBuilder().setEnabled(enabled)
+                    // TODO: Before Multihop is supported on Android, calling `setDirectOnly` with false
+                    // will cause undefined behaviour.
+                    .setDirectOnly(true)
+                    .build()
+            grpc.setDaitaSettings(daitaSettings)
+        }
             .mapLeft(SetDaitaSettingsError::Unknown)
             .mapEmpty()
 

mullvad-types/src/wireguard.rs

@@ -81,14 +81,35 @@ impl FromStr for QuantumResistantState {
 pub struct QuantumResistantStateParseError;
 
 #[cfg(daita)]
-#[derive(Debug, Default, Clone, Serialize, Deserialize, PartialEq)]
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct DaitaSettings {
     pub enabled: bool,
 
-    #[serde(default)]
+    #[serde(default = "DaitaSettings::default_use_multihop_if_necessary")]
+    /// Whether to use multihop if the selected relay is not DAITA-compatible. Note that this is
+    /// the inverse of of "Direct only" in the GUI.
     pub use_multihop_if_necessary: bool,
 }
 
+#[cfg(daita)]
+impl DaitaSettings {
+    const fn default_use_multihop_if_necessary() -> bool {
+        cfg!(not(target_os = "android"))
+    }
+}
+
+#[cfg(daita)]
+impl Default for DaitaSettings {
+    fn default() -> Self {
+        Self {
+            enabled: false,
+            // This setting should be enabled by default, expect on Android where multihop is not
+            // supported.
+            use_multihop_if_necessary: Self::default_use_multihop_if_necessary(),
+        }
+    }
+}
+
 /// Contains account specific wireguard data
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
 pub struct WireguardData {