added Mass Assignment feature

- added u_fillable on models used in tests that need it
 - added documentation for mass assignment
 - added tests for mass assignment feature
 - added new Torrent models for tests, which have set up u_fillable and
   u_guarded differently
 - added schema grammar, query post-processor, and schema builder, they
   was needed for database column listing during a mass assignment
   guarded attributes check, used to check if the given attribute is
   a valid guardable column

src/orm/sqliteconnection.cpp

@@ -1,6 +1,9 @@
 #include "orm/sqliteconnection.hpp"
 
 #include "orm/query/grammars/sqlitegrammar.hpp"
+#include "orm/query/processors/sqliteprocessor.hpp"
+#include "orm/schema/grammars/sqlitegrammar.hpp"
+#include "orm/schema/sqlitebuilder.hpp"
 
 #ifdef TINYORM_COMMON_NAMESPACE
 namespace TINYORM_COMMON_NAMESPACE
@@ -20,13 +23,35 @@ SQLiteConnection::SQLiteConnection(
        of the database abstraction, so we initialize it to the default value
        while starting. */
     useDefaultQueryGrammar();
+
+    useDefaultPostProcessor();
+}
+
+std::unique_ptr<SchemaBuilder> SQLiteConnection::getSchemaBuilder()
+{
+    if (!m_schemaGrammar)
+        useDefaultSchemaGrammar();
+
+    return std::make_unique<Schema::SQLiteBuilder>(*this);
 }
 
 std::unique_ptr<QueryGrammar> SQLiteConnection::getDefaultQueryGrammar() const
 {
+    // FEATURE table prefix silverqx
     return std::make_unique<Query::Grammars::SQLiteGrammar>();
 }
 
+std::unique_ptr<SchemaGrammar> SQLiteConnection::getDefaultSchemaGrammar() const
+{
+    // FEATURE table prefix silverqx
+    return std::make_unique<Schema::Grammars::SQLiteGrammar>();
+}
+
+std::unique_ptr<QueryProcessor> SQLiteConnection::getDefaultPostProcessor() const
+{
+    return std::make_unique<Query::Processors::SQLiteProcessor>();
+}
+
 } // namespace Orm
 #ifdef TINYORM_COMMON_NAMESPACE
 } // namespace TINYORM_COMMON_NAMESPACE