Use extra property to determine the content of messages

app/src/main/java/com/github/gotify/messages/Extras.java

@@ -0,0 +1,21 @@
+package com.github.gotify.messages;
+
+import com.github.gotify.client.model.Message;
+import java.util.Map;
+
+public final class Extras {
+    private Extras() {}
+
+    public static boolean useMarkdown(Message message) {
+        if (message.getExtras() == null) {
+            return false;
+        }
+
+        Object display = message.getExtras().get("client::display");
+        if (!(display instanceof Map)) {
+            return false;
+        }
+
+        return "text/markdown".equals(((Map) display).get("contentType"));
+    }
+}

app/src/main/java/com/github/gotify/messages/ListMessageAdapter.java

@@ -74,7 +74,11 @@ public class ListMessageAdapter extends BaseAdapter {
         }
         ViewHolder holder = new ViewHolder(view);
         final MessageWithImage message = items.get(position);
+        if (Extras.useMarkdown(message.message)) {
             markwon.setMarkdown(holder.message, message.message.getMessage());
+        } else {
+            holder.message.setText(message.message.getMessage());
+        }
         holder.title.setText(message.message.getTitle());
         picasso.load(Utils.resolveAbsoluteUrl(settings.url() + "/", message.image))
                 .error(R.drawable.ic_alarm)