WIP DateTypeConverter実装

source/src/main/java/one/nem/lacerta/source/database/common/DateTypeConverter.java

@@ -1,4 +1,16 @@
 package one.nem.lacerta.source.database.common;
 
+import androidx.room.TypeConverter;
+
 public class DateTypeConverter {
+
+    @TypeConverter
+    public static java.util.Date fromTimestamp(Long value) {
+        return value == null ? null : new java.util.Date(value);
+    }
+
+    @TypeConverter
+    public static Long dateToTimestamp(java.util.Date date) {
+        return date == null ? null : date.getTime();
+    }
 }