ui,tunnel: support DNS search domains

wg-quick has supported this for a while, but not the config layer, and
not the Go backend, so wire this all up.

Requested-by: Alexis Geoffrey <alexis.geoffrey97@gmail.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/src/main/java/com/wireguard/android/databinding/BindingAdapters.kt

@@ -152,6 +152,12 @@ object BindingAdapters {
         view.text = if (addresses != null) Attribute.join(addresses.map { it?.hostAddress }) else ""
     }
 
+    @JvmStatic
+    @BindingAdapter("android:text")
+    fun setStringSetText(view: TextView, strings: Iterable<String?>?) {
+        view.text = if (strings != null) Attribute.join(strings) else ""
+    }
+
     @JvmStatic
     fun tryParseInt(s: String?): Int {
         if (s == null)

ui/src/main/java/com/wireguard/android/viewmodel/InterfaceProxy.kt

@@ -81,7 +81,7 @@ class InterfaceProxy : BaseObservable, Parcelable {
 
     constructor(other: Interface) {
         addresses = Attribute.join(other.addresses)
-        val dnsServerStrings = other.dnsServers.map { it.hostAddress }
+        val dnsServerStrings = other.dnsServers.map { it.hostAddress }.plus(other.dnsSearchDomains)
         dnsServers = Attribute.join(dnsServerStrings)
         excludedApplications.addAll(other.excludedApplications)
         includedApplications.addAll(other.includedApplications)