Add CapabilityAwarePayload interface

network/src/main/java/io/bitsquare/p2p/storage/payload/CapabilityAwarePayload.java

@@ -0,0 +1,18 @@
+package io.bitsquare.p2p.storage.payload;
+
+import io.bitsquare.common.wire.Payload;
+
+import java.util.List;
+
+/**
+ * Used for messages which require that the data owner is online.
+ * <p>
+ * This is used for the offers to avoid dead offers in case the offerer is in standby mode or the app has
+ * terminated without sending the remove message (e.g. network connection lost or in case of a crash).
+ */
+public interface CapabilityAwarePayload extends Payload {
+    /**
+     * @return Capabilities the other node need to support to receive that message
+     */
+    List<Integer> getRequiredCapabilities();
+}