Try to implement H2

src/main/java/fr/xephi/authme/initialization/DataSourceProvider.java

@@ -5,6 +5,7 @@ import fr.xephi.authme.data.auth.PlayerCache;
 import fr.xephi.authme.datasource.CacheDataSource;
 import fr.xephi.authme.datasource.DataSource;
 import fr.xephi.authme.datasource.DataSourceType;
+import fr.xephi.authme.datasource.H2;
 import fr.xephi.authme.datasource.MariaDB;
 import fr.xephi.authme.datasource.MySQL;
 import fr.xephi.authme.datasource.PostgreSqlDataSource;
@@ -76,6 +77,9 @@ public class DataSourceProvider implements Provider<DataSource> {
             case SQLITE:
                 dataSource = new SQLite(settings, dataFolder);
                 break;
+            case H2:
+                dataSource = new H2(settings, dataFolder);
+                break;
             default:
                 throw new UnsupportedOperationException("Unknown data source type '" + dataSourceType + "'");
         }