Oracle v11 and newer: No schema name convertion to Upper case

Don't know whethere it should be for all the versions so left them as they were.
The v11 does not require shemas to be upper case for sure

Author: alex-kulakov

Orm/Xtensive.Orm.Oracle/Sql.Drivers.Oracle/v09/Extractor.cs

@@ -45,7 +45,7 @@ public override Schema ExtractSchema(string catalogName, string schemaName)
     {
       targetSchemes.Clear();
       theCatalog = new Catalog(catalogName);
-      var targetSchema = schemaName.ToUpperInvariant();
+      var targetSchema = ToUpperInvariantIfNeeded(schemaName);
       targetSchemes.Add(targetSchema);
 
       RegisterReplacements(replacementsRegistry);
@@ -60,7 +60,7 @@ public override Catalog ExtractSchemes(string catalogName, string[] schemaNames)
       theCatalog = new Catalog(catalogName);
       targetSchemes.Clear();
       foreach (var schemaName in schemaNames) {
-        var targetSchema = schemaName.ToUpperInvariant();
+        var targetSchema = ToUpperInvariantIfNeeded(schemaName);
         targetSchemes.Add(targetSchema);
       }
 
@@ -71,6 +71,11 @@ public override Catalog ExtractSchemes(string catalogName, string[] schemaNames)
       return theCatalog;
     }
 
+    protected virtual string ToUpperInvariantIfNeeded(string schemaName)
+    {
+      return schemaName.ToUpperInvariant();
+    }
+
     private void ExtractCatalogContents()
     {
       ExtractTables();
@@ -92,7 +97,7 @@ private void ExtractSchemas()
         while (reader.Read())
           theCatalog.CreateSchema(reader.GetString(0));
       // choosing the default schema
-      var defaultSchemaName = Driver.CoreServerInfo.DefaultSchemaName.ToUpperInvariant();
+      var defaultSchemaName = ToUpperInvariantIfNeeded(Driver.CoreServerInfo.DefaultSchemaName).ToUpperInvariant();
       var defaultSchema = theCatalog.Schemas[defaultSchemaName];
       theCatalog.DefaultSchema = defaultSchema;
     }

Orm/Xtensive.Orm.Oracle/Sql.Drivers.Oracle/v11/Extractor.cs

@@ -13,6 +13,8 @@ internal class Extractor : v10.Extractor
   {
     // Constructors
 
+    protected override string ToUpperInvariantIfNeeded(string schemaName) => schemaName;
+
     public Extractor(SqlDriver driver)
       : base(driver)
     {