Store additional data that will allow us to reduce the number of verification SMSs.

core-util/src/main/java/org/signal/core/util/Serializer.kt

@@ -15,3 +15,15 @@ interface IntSerializer<T> : Serializer<T, Int>
 interface LongSerializer<T> : Serializer<T, Long>
 
 interface ByteSerializer<T> : Serializer<T, ByteArray>
+
+object StringStringSerializer : StringSerializer<String?> {
+
+  override fun serialize(data: String?): String {
+    return data ?: ""
+  }
+
+  override fun deserialize(data: String): String {
+    return data
+  }
+
+}