Finalize wallpaper UX.

Co-authored-by: Greyson Parrelli <greyson@signal.org>
Co-authored-by: Alan Evans <alan@signal.org>

app/src/main/java/org/thoughtcrime/securesms/recipients/Recipient.java

@@ -855,6 +855,10 @@ public class Recipient {
     }
   }
 
+  public boolean hasOwnWallpaper() {
+    return wallpaper != null;
+  }
+
   /**
    * A cheap way to check if wallpaper is set without doing any unnecessary proto parsing.
    */