Make the max pool size configurable

common/src/main/java/me/lucko/luckperms/common/config/AbstractConfiguration.java

@@ -130,7 +130,8 @@ public abstract class AbstractConfiguration<T extends LuckPermsPlugin> implement
                 getString("data.address", null),
                 getString("data.database", null),
                 getString("data.username", null),
-                getString("data.password", null)
+                getString("data.password", null),
+                getInt("data.pool-size", 10)
         );
         storageMethod = getString("storage-method", defaultStorage);
         splitStorage = getBoolean("split-storage.enabled", false);

common/src/main/java/me/lucko/luckperms/common/storage/DatastoreConfiguration.java

@@ -33,5 +33,6 @@ public class DatastoreConfiguration implements me.lucko.luckperms.api.data.Datas
     private final String database;
     private final String username;
     private final String password;
+    private int poolSize;
 
 }

common/src/main/java/me/lucko/luckperms/common/storage/backing/MySQLBacking.java

@@ -56,8 +56,9 @@ public class MySQLBacking extends SQLBacking {
         final String database = configuration.getDatabase();
         final String username = configuration.getUsername();
         final String password = configuration.getPassword();
+        
+        config.setMaximumPoolSize(configuration.getPoolSize());
 
-        config.setMaximumPoolSize(10);
         config.setPoolName("luckperms");
         config.setDataSourceClassName("com.mysql.jdbc.jdbc2.optional.MysqlDataSource");
         config.addDataSourceProperty("serverName", address.split(":")[0]);