Disable the automatic poolSize option

it creates more issues than benefits

src/main/java/fr/xephi/authme/settings/SettingsMigrationService.java

@@ -70,6 +70,7 @@ public class SettingsMigrationService extends PlainMigrationService {
             | performMailTextToFileMigration(resource)
             | migrateJoinLeaveMessages(resource)
             | migrateForceSpawnSettings(resource)
+            | migratePoolSizeSetting(resource)
             | changeBooleanSettingToLogLevelProperty(resource)
             | hasOldHelpHeaderProperty(resource)
             | hasSupportOldPasswordProperty(resource)
@@ -194,6 +195,21 @@ public class SettingsMigrationService extends PlainMigrationService {
             | moveProperty(oldForceWorlds, FORCE_SPAWN_ON_WORLDS, resource);
     }
 
+    /**
+     * Detects the old auto poolSize value and replaces it with the default value.
+     *
+     * @param resource The property resource
+     * @return True if the configuration has changed, false otherwise
+     */
+    private static boolean migratePoolSizeSetting(PropertyResource resource) {
+        Integer oldValue = resource.getInt("DataSource.poolSize");
+        if(oldValue == null || oldValue > 0) {
+            return false;
+        }
+        resource.setValue("DataSource.poolSize", 10);
+        return true;
+    }
+
     /**
      * Changes the old boolean property "hide spam from console" to the new property specifying
      * the log level.

src/main/java/fr/xephi/authme/settings/properties/DatabaseSettings.java

@@ -123,9 +123,9 @@ public final class DatabaseSettings implements SettingsHolder {
     public static final Property<String> MYSQL_COL_GROUP =
         newProperty("ExternalBoardOptions.mySQLColumnGroup", "");
 
-    @Comment("Overrides the size of the DB Connection Pool, -1 = Auto")
+    @Comment("Overrides the size of the DB Connection Pool, default = 10")
     public static final Property<Integer> MYSQL_POOL_SIZE =
-        newProperty("DataSource.poolSize", -1);
+        newProperty("DataSource.poolSize", 10);
 
     @Comment({"The maximum lifetime of a connection in the pool, default = 1800 seconds",
         "You should set this at least 30 seconds less than mysql server wait_timeout"})