Fix messaging [WIP] (#1614)

* Fix messaging [WIP]

* Make codeclimate happy

* Codeclimate, pls

* got it, i hope

* Improvements

* Remove duplicated checks, other improvements, make login/logout broadcasts

* Optimize project imports

* Make codeclimate happy again

src/main/java/fr/xephi/authme/datasource/CacheDataSource.java

@@ -71,6 +71,11 @@ public class CacheDataSource implements DataSource {
         source.reload();
     }
 
+    @Override
+    public boolean isCached() {
+        return true;
+    }
+
     @Override
     public boolean isAuthAvailable(String user) {
         return getAuth(user) != null;

src/main/java/fr/xephi/authme/datasource/DataSource.java

@@ -14,6 +14,15 @@ import java.util.Set;
  */
 public interface DataSource extends Reloadable {
 
+    /**
+     * Return whether the data source is cached and needs to send plugin messaging updates.
+     *
+     * @return true if the data source is cached.
+     */
+    default boolean isCached() {
+        return false;
+    }
+
     /**
      * Return whether there is a record for the given username.
      *